Riley McCarron never stood much of a chance to stick around in the NFL. But that’s part of what makes him a Patriots’ prototype.

An undersized slot receiver, McCarron slipped onto the Patriots practice squad a few weeks after the departure of slot receiver Austin Carr, who led the Patriots in receptions and receiving yards during the preseason. Carr’s preseason performance propelled him onto the New Orleans Saints roster after winning over the hearts of countless New Englanders who thought he’d be the next Julian Edelman. Amid the disappointment of Carr’s departure, Patriots fans may have missed the arrival of McCarron.

During the 2017 training camp, Texans coach Bill O’Brien dubbed McCarron the “spitting image” of Wes Welker when McCarron was trying to make Houston’s roster. The Patriots nabbed the rookie when Houston released him in September.

The 5-foot-9 McCarron fits the bill to be New England’s next slot receiver. Sure, the chances are slim — very slim. But that’s just one box players have to check to be the next man up at slot receiver with the Patriots. Danny Amendola and Welker were all undrafted free agents out of college. Edelman was a seventh rounder. They all had slim chances like McCarron, a former undrafted player out of Iowa.

Formerly undrafted. Formerly a walk-on.

McCarron joined the Iowa Hawkeyes without a football scholarship. He wasn’t even trying to earn one. All he cared about was getting playing time.

“The whole point of playing college football is to play,” McCarron said.

When he made the Iowa team and was awarded a scholarship, he started as a redshirt his freshman year, then began to contribute on special teams. He slowly moved his way into the offensive unit.

By his senior season, he’d risen to the second spot on the depth chart. And then in September, an injury befell Matt VandeBerg, the team’s top receiver. McCarron responded with 42 receptions for four touchdowns and 517 receiving yards, a team-high. He played in 14 games and started one.

His numbers at Iowa were not gaudy, but the Hawkeyes don’t exactly run an air raid offense. In McCarron’s final year, Iowa quarterback C.J. Beathard passed for an average of 148 yards a game.

In an offense focused on running the football, McCarron wasn’t playing his way into the top rounds of the NFL draft. But he did earn the respect of his teammates.

“If you ask him to go block a linebacker, he’ll do it,” said Cole Croston, who is a Patriots’ rookie and former undrafted free agent out of Iowa like McCarron.

McCarron was nasty like an Iowa lineman. But he was also a playmaker.

“One of those guys you could tell instantly he was a special player, but you could see how he got overlooked just because of his height,” said Patriots center James Ferentz, who played with McCarron for two years at Iowa. James is also Iowa coach Kirk Ferentz’s son. “You could always see these flashes. Always around the ball. Good hands. … He’s football fast. He’s shifty. Good in-game speed.”

His college production may pale in comparison to his predecessors but his measurables do not.

With such little production to show for his college years, McCarron began working for an accounting firm in Chicago after leaving Iowa. He admitted he’d given up on his future in football. So his life went on without it — briefly.

After just four days at the firm, he spoke to his bosses about returning to Iowa City to train for his Pro Day. They approved his request — they didn’t even make him give two weeks notice.

“It was a crazy experience,” he said. “I was thinking that if I did Pro Day and no one called, then at least I did it. At least it was peace of mind. I could always look back and say I tried. But if I looked back and didn’t even say I gave it a shot, I probably would have had some regret.”

McCarron finished with a 4.36-second 40-yard dash, a 6.47-second 3-cone drill and a 40.5 inch vertical leap. That leap, perhaps, could make up for his lack of height. That speed and agility could complement his 188-pound frame. For those unfamiliar with those speed and agility measurements, McCarron’s 40-yard dash time and 3-cone drill time ware faster than those of Edelman, Welker and Amendola. The 3-cone drill has been one to which Bill Belichick seems to pay close attention.

The Patriots didn’t have McCarron in for training camp. Instead, he ended up with the Texans, where O’Brien referred to McCarron as the “Iowa flash.” That’s when McCarron spent time working with Welker, who is a receivers coach for the Texans.

“Every day that we were practicing or in the facility was time with Wes,” McCarron said. “His knowledge of the game is incredible — just things that I would have never thought about, had he not informed me or coached me. To bring that to the field while I was in Houston was big. And then even the things that I learned when I got here. I could see a lot of the translation to what he was coaching and what they were doing up here. It was a really big benefit for me at this point in my career.”

With Welker’s wisdom, McCarron joined the Patriots. And while he didn’t overlap with Edelman, who tore his ACL before McCarron arrived, McCarron began learning from another Welker clone: Amendola.

“Obviously, me and Danny have kind of the same build,” McCarron said. “He’s in the slot, too. Any chance I can, I’ll try to pick his brain, ask him why he does one thing instead of another. I keep learning, and he always has an answer for something. … Trying to learn any way I can, especially guys who have done it and proven themselves for a long period of time.”

Amendola said McCarron is a talented young receiver eager to learn. When asked whether McCarron might be another productive slot receiver in the making, Amendola wouldn’t crown the 24-year-old the prince of the slot.

“It’s up to him, really. The opportunity is here for him,” Amendola said.

He pointed out just how much it takes to go from the undrafted rookie to being Tom Brady’s trusted target. “It takes a lot,” Amendola said.

It takes a mastery of New England’s complicated playbook. It takes reps with Brady during practice, which likely McCarron isn’t getting as a practice squad player. It takes offseason workouts with Brady, which are invite-only. It takes preseason and regular season action.

“When you’re not the guy, you’ve got to be willing to grind it out,” said Patriots backup quarterback Brian Hoyer, who was also an undrafted free agent. “Take every rep you can and take advantage of those reps when they come. Even Julian, you look at where he’s gotten to — think of the iconic catches he’s made in the Super Bowl.

“I remember when we were rookies (in 2009). He’s just trying to do everything he can just to get one rep with Tom. But that’s what it takes. Julian is so driven, and that’s why it’s been so fun — as a friend of his — to see where he’s gotten to, and to make those catches he’s made, because I know how hard he’s worked to get there. When I look at Riley, he’s working just as hard as he can to get better and then take advantage of those opportunities when they present themselves.”

For now, he’ll have to prove it on the scout team

McCarron has started with step 1: the playbook.

“I’m just trying to learn the offense and get it down,” McCarron said. “Trying to get more comfortable with it. That comes with time and studying the playbook. … It’s definitely a challenge, just like anything else. It’s starting to feel a little bit more comfortable than when I first got here. So hopefully that continues, because that slows things down so you can play a little faster. So far, so good.”

If he’s had any major setbacks, they haven’t been apparent. Reporters aren’t allowed to watch more than the warmups of Patriots practices, but McCarron has apparently been working to the coach’s satisfaction. He has twice been named practice player of the week. He did so after the Patriots’ Week 12 win over the Miami Dolphins when he was tasked with emulating Jarvis Landry, one of the league’s elite slot receivers.

Croston, who is on the active roster and lives with McCarron, has been impressed with his housemate.

“It’s an impressive feat in itself,” Croston said of the practice player awards. “That speaks to his work ethic and the pride he takes in his job. And I think that translates all the way back to what he was doing at Iowa. We were scout team guys at Iowa, too. The only way to work your way up is to start from the bottom.”

He doesn’t seem like he’s skipping steps either. McCarron, who said he’s keeping his head down to stay hard at work, is working to earn the trust of Hoyer, the scout team quarterback.

“I’ve developed some chemistry with (Hoyer) since he got here,” McCarron said. “Just so people can count on you. If the team can’t count on you, you really might be out of a job.”

And that’s the harsh reality of McCarron’s quest to be the next Patriots’ slot receiver. He’s more likely to get cut than he is to finish the 2019 season with 60 catches. McCarron has a long way to go. But the path has been well-paved by players just like him.