SAN ANTONIO -- Clutching a Sharpie at an Academy sporting goods on a balmy Sunday, San Antonio Spurs rookie guard Jonathon Simmons squinted carefully at the almost 500 fans waiting in line for autographs.

The longer he peered into the crowd, the faster Simmons drifted into the daydream; this cotton-candy fantasy spun fresh every day with every jumper and dunk, with every well-wisher's text message, practically every moment.

"Really, that's what it felt like: a daydream," Simmons recalled. "To see almost 500 people just waiting on me, it was like, 'What?' It was crazy that people wanted to come out and see me; not because I'm a Spurs player, but actually because people like the way I play. Like, I'm really sitting here, and a whole line of people are here for me to just sign autographs. I never thought that day would come."

Nobody did.

Then again, few successfully navigate the route Simmons charted toward the NBA. He walked into a gym at Concordia College in September of 2013 and plopped down a $150 registration fee to join an open NBA Development League tryout involving approximately 60 players. Now after two successful seasons in the D-League, Simmons is a serious rotational contributor on a championship contender.

At the very least, improbable, but in most scenarios, it's impossible.

"It takes different people different paths," Spurs general manager R.C. Buford told ESPN.com. "Clearly, his wasn't linear."

One last shot at NBA

This story came dangerously close to never being told because Simmons nearly gave up on his NBA dream.

He grew up in the hardscrabble Fifth Ward neighborhood on the northeast side of Houston, earning co-most valuable player recognition at M.B. Smiley High School. Simmons later spent time at two different junior colleges before signing with the University of Houston, where he sat out his first season due to NCAA transfer rules.

At Houston, Simmons played in 30 games, averaging 14.7 points, 5.0 rebounds and 2.2 assists. But he decided not to stick around for his senior season, in part because he had four mouths to feed, four precious daughters. So Simmons declared for the NBA draft, which proved to be a bad move.

Simmons averaged 15.2 points a game last season for the Spurs' D-League affiliate in Austin. Layne Murdoch/Getty Images

"After the draft process, I didn't even get invited to a summer league team," Simmons said. "I felt like I had a decent enough of a college season. Of course, it wasn't a good idea to just leave. But I wasn't happy there. So I'd rather take the chance of just going pro instead of having to transfer or sit out. I wasn't happy at U of H with the coaching and all that stuff.

"What was going through my head was really just how I was gonna make it. I was really just worried about how I was going to feed my family. I think that was the main thing going through my head. Should I just go and get a job? Or should I continue to play basketball? Even when it was hard, my mom helped me a lot with the kids. It just made it a lot easier for me to not just give up because I had people that believed in me more than I believed in myself. My mama raised me to be a man. Handle your business. So if you make a decision, deal with your decision. You have to make the best of it."

That led to playing his first professional basketball season with the Sugar Land Legends of the American Basketball League, where he averaged 36.5 points in 16 games.

"I almost quit after that," Simmons said. "Before the first season of D-League, I played in the ABL and was like, 'This can't be what basketball is about.' I really wasn't exposed to overseas [basketball], and I really only watched NBA. In my era, we never really had anybody come and explain anything to us [about the process of making it to the NBA]. I never really met scouts. I just didn't know about any of this type of stuff. All I knew was either you're gonna go to school or just go to work. That's where I was."

A talented barber who cuts his friends' hair on occasion, Simmons considered a career change. His mother told him if he was done with basketball, he should try to get his barber's license and find a real job.

But Simmons decided to give the game one last try, which led to the tryout at Concordia University in Austin, Texas, with San Antonio's D-League affiliate, then nicknamed the Austin Toros. For a $150 tryout registration fee, Simmons got another chance to show the Spurs organization what he could do.

"At that point, it did kind of seem strange because I had worked out for them during the draft process the year prior," Simmons said. "San Antonio does its summer workouts in September. Like I was actually down here for a whole week of that, then had to go to the camp after that. So it was really strange that they still wanted me to go try out for them after they had seen me a whole week prior to that."

The tryout went well enough that the Austin Toros immediately invited him back for a weeklong tryout session, and he eventually made the opening-night roster. Austin Spurs GM Brian Pauga told the Spurs' official website, "It didn't take long to see he was head and shoulders above the others in that tryout."

With the Toros, Simmons played for coaches Ken McDonald, Earl Watson, Jason Fraser and Mike Miller, who all worked diligently to elevate his game.

"There's a lot of places along the way where a guy in Jonathon's shoes could have fallen off the path. But he believed in himself." R.C. Buford on Jonathon Simmons

"They just stayed on me every day," Simmons said. "It was just surprising that guys you barely have a relationship with show so much support and see so much in you. So it was kind of tough for me to understand because where I come from, you don't trust too many people."

Simmons averaged almost 10 points his first season in the D-League, which led to several calls from McDonald and Watson to Buford about the guard's ability as a potential San Antonio Spur. Buford admitted the Spurs didn't view Simmons with the same reverence as Watson -- now the interim coach of the Phoenix Suns -- and McDonald.

"There's a lot of places along the way where a guy in Jonathon's shoes could have fallen off the path," Buford said. "But he believed in himself. I think the coaches in Austin probably recognized it sooner than we did. Ken McDonald, Earl Watson, those guys were speaking about Jonathon in ways that none of us believed initially, a year and a half ago. But he kept playing. He kept fighting. The guys in Austin started making us pay attention 15 games into the D-League season a year ago. They really kept hounding us, [saying], 'He's making progress. He's getting things done. He's got a different level of athleticism.'

"I think Earl was probably a big factor in that because Earl's path wasn't necessarily linear."

In Simmons' second D-League season, he averaged 15.2 points, 4.3 rebounds and 3.0 assists on the way to earning recognition as an All-D-League defender. By July 2015, Simmons was playing for the Brooklyn Nets' summer league team when he got the call he had always dreamed about.

Simmons was on the team bus about to go to a summer league game in Orlando, Florida, when his agent called.

"Jon, you are now an NBA player," he told Simmons, who was confused until he learned that the Spurs had given him a two-year deal.

He played on the Spurs' summer league team in Las Vegas, where he scored 23 points in the championship game, leading the Spurs to a title while winning MVP honors.

"Getting in front of Pop and the coaches this summer in the minicamp, he just had a different athleticism than what our guys had," Buford said. "We felt like having somebody that could play downhill and break down defenses was important. He worked at it hard enough that we hoped it could work. But the credit needs to go to Jonathon because there are places all along that journey that could have caused things to go wrong."

A 'fearless' addition to the Spurs

A 26-year-old rookie, Simmons might provide a snapshot into San Antonio's future. Tony Parker, Manu Ginobili and Tim Duncan won't play forever, and the Spurs already seem to be in the midst of ushering in the coming years with younger players such as Kawhi Leonard, LaMarcus Aldridge and Danny Green, not to mention Simmons and Kyle Anderson.

Jonathon Simmons comes off the bench to give the Spurs an athletic and versatile guard who won't back down defensively. Gary Dineen/Getty Images

"He's pretty fearless. He just goes and plays, kind of like Manu," Popovich said. "He just dives into the game, and he competes. He really has great athletic skills. He's learning the game, and he's a quick learner, good worker. So he's got a chance to be a long-time player in the league if he pays attention and sticks to it."

Whether it's defending against Kyrie Irving, LeBron James or Golden State's Stephen Curry, Simmons relishes the challenge and attacks it with a level of confidence not typically seen among rookies, especially players coming off a two-year stint in the D-League.

Simmons admits it took nearly a month into his first NBA season to find his swagger.

"The path that Jonathon took, I don't know that he necessarily believed that, Feb. 1, he would be where he is, even in training camp," Buford said. "His play has grown. His confidence has grown. I think his internal belief has grown because there were times I think he didn't play with the confidence and purpose in training camp that someone who knew they were gonna make it. When you've been told you're not gonna make it for a long time, there are a lot of places where doubt can creep in."

Simmons worked hard to prevent that from happening, but there were occasions when it did. Three days before Thanksgiving, everything finally started to click for Simmons in a 94-84 win over the Phoenix Suns, when he contributed only one field goal in seven minutes of action.

"I scored one bucket, but until that point, even a couple of games before I actually played, I was just telling myself like, 'OK, you're ready now,'" Simmons said. "Plus, this is a confidence league. When I figured it out, and felt like I know I can play, that's all it took for me to just say to myself, 'OK, I can do it every night.' It just took that one time for me to just show I can do it. So every time out there now, I'm just trying to make the best of my opportunity."

A demanding coach such as Popovich grants few of those. So every second on the court provides a precious opportunity to gain the coach's trust. Sure, Simmons possesses enough explosiveness and athleticism to break down defenses. But San Antonio's roster already contains plenty of offensive playmakers. So, if you want to impress Popovich, play defense. Luckily for Simmons, that's his specialty.

"It's tough because we're playing to win a championship," Parker said. "They say Pop is very demanding, [and he has] high expectations. You can't [make] any mistakes, especially if you come off the bench. So for some of the guys, it's kind of tough because when you come in, you have to perform right away to earn his trust and for him to feel comfortable to put you out there.

"When you first come, I think the best way to start and earn his confidence is to stop your guy and play great defense. It almost doesn't matter about the offense, it's just defensively, [he has to feel] he can trust you that you're gonna not make any mistakes. Then, you have a better chance to play more."

"Shoot, every day I kind of think and just reflect back on all it took to get to this point. I'm just continuing to stay humble about it because I want to keep getting better."

Simmons recognized this quickly and executed. In turn, the confidence grew.

Over the past three weeks, Simmons has matched up against childhood idol Kobe Bryant, Curry, James and Irving, producing varying levels of success. In those matchups, Simmons never displayed one iota of fear.

"I've always been able to play defense," he said. "I think defense is just effort. You don't have to have a lot of skill to play defense. It's just effort. So I just tried to bring it on defense, and sharpen up my tools on offense. Raw, I've heard that so many times about my skills. But I'm just not scared of a challenge. I'm not scared of somebody telling me, 'Hey, you can't guard him.' I've been told stuff like that my whole life. It just goes in one ear and out the other.

"Even just watching these dudes on TV, I know how I am. I know how you have to be, especially as a defender. You can't just let guys be comfortable. If they're comfortable, they'll tear you up. You see what Steph Curry does every night. So you just can't let them get comfortable. I just take pride in my defense, especially one-on-one defense. You're just not gonna shake me and blow by me. I really take pride in that. Plus, we're on national TV, and I'm not about to have anybody calling me talking about, 'Oh, Kyrie got you.' I take pride in stuff like that. I don't like being embarrassed."

Earning the Spurs' trust

When Simmons arrived in San Antonio over the summer for open gym, he quickly befriended veteran Rasual Butler, who took the rookie under his wing, despite the fact the two very well could have been competing for the same roster spot.

That relationship still floors Buford, but Butler, whose winding path through the NBA is similar to Simmons', shared a kinship with the rookie guard.

It takes time to earn Gregg Popovich's trust, and Simmons has made great strides as a rookie. Chris Covatta/Getty Images

"It gives you more incentive to foster that relationship when the guy has all the talent like he has," Butler said. "He has the ability to be a really special player at this level because of his versatility as a wing player, the way he defends, his athleticism. Him being here is the perfect place for him to kind of raise his basketball IQ. He already has a high basketball IQ, but you have to kind of harness him a little because he's so athletic, young and excited about living his dream, that you've got to just tell him to settle down and be solid right now just because of the way our team is structured with certain guys we're going to feature. So you've got to kind of fit in and be aggressive without being in their way."

Popovich said as much on Dec. 3 before the team's win over the Memphis Grizzlies.

"Players earn your trust by playing well and not making mistakes," he said. "It's always tougher for people off the bench and for younger players, because they're under a different type of microscope. Timmy Duncan can go make mistakes and we'll talk about it. He'll probably be allowed to make a few before I'm going to do anything about it. Young kids and subs, they've got to be possibly more focused than starters in a sense when they come out. They understand the priorities and what wins and loses games, and it takes a while for them to figure that out.

"We make that very clear to them, and Jonathon, for one, has come a long way in understanding that we don't need to know how great he might be. We just want him to be solid. If he's solid, he can show us how great he is down the road sometime in the future."

So for right now, that's the plan for Simmons. Until then, he'll continue to dream.

Simmons' mother, LaTonya, raised Jonathon and his three siblings (his sister Joi plays college basketball at Xavier), on a salary working the gate taking tickets for United Airlines at George Bush Intercontinental Airport. A Spurs ball dangles off LaTonya's walkie-talkie, often sparking conversation for her to proudly inform folks of Jonathon's success.

Simmons receives a call from LaTonya just about every time such an interaction takes place at the airport. That causes Jonathon to start dreaming again. Same thing when friends text congratulatory messages after seeing him on TV defending NBA stars. It's the same thing, night after night, when he pulls on that No. 17 Spurs jersey.

In those tense moments before tipoff, "in my mind, I'm thinking about how I want to be almost perfect, especially on defense," Simmons said. "In my heart, I just want to have fun doing something I love to do."

Looking up at the rafters inside the team's practice facility, Simmons squints again, realization for probably the 100th time that day he's actually living his NBA dream.

"Shoot, every day I kind of think and just reflect back on all it took to get to this point. I'm just continuing to stay humble about it because I want to keep getting better, and being the new guy, I just want to try to get the respect from the other guys," Simmons said. "This was just about turning negatives into positives for me, and just appreciating the experience. I always talked about it. But I think it wasn't until after my first year in the D-League where I really got comfortable enough to feel like someday I'm going to be a big part of this team. I know what I can do."