WALTHAM, Mass. -- James Young hears all the noise; it's impossible to avoid. Sometimes all he has to do is venture into his Twitter mentions and someone will have passed along a link to a story about him like one recent blog titled, "Does James Young have the work ethic to succeed in the NBA?"

The court of public opinion seems to have decided that Young's inability to crack the Boston Celtics' rotation during his rookie season suggests that he doesn't have the desire to work for a role. When former teammates visit for draft workouts, they are quizzed about Young's desire. The 19-year-old Young, the No. 17 pick in the 2014 draft, squeezes his palms together tightly when presented this information and shakes his head.

"I see it, I hear it," Young told ESPN.com after a recent morning workout at the Celtics' training facility. "It just motivates me. When they talk about me like that -- man, I got here for a reason. I have the drive. I'm not worried about anything. I'm just out here trying to get better."

Here's what most haven't seen: If the Celtics maintained a leaderboard for offseason hours in the gym, Young would be near the top. A familiar presence since the end of the season, he often engages in two-a-day sessions at the team's training facility. The results? He's carrying 15 pounds of additional muscle, has trimmed his body fat and has added three inches to his vertical over the past year, the fruits of a newfound dedication to the weight room.

James Young averaged 3.4 points in 31 games as a rookie with the Celtics this season. Brian Babineau/NBAE/Getty Images

Young admits his work ethic might not have been at the level it needed to be when he arrived in the NBA. The weight room wasn't a top priority for a player who previously got by on pure skill and athleticism. But what a sobering rookie experience taught him was that he needed to get stronger to defend multiple positions, that he had to find new ways to generate his own offense, and that he had to work harder than he ever had to simply get on the floor.

And to be absolutely certain, Young is putting in the effort.

"I think he's really worked," Celtics coach Brad Stevens said. "Individually, he's always been a guy that's gotten in and worked. I thought the guys that have worked with him have done a really good job. You can see the strides -- it's clear as day."

Echoes Celtics president of basketball operations Danny Ainge: "James has really really matured -- physically and mentally -- and we're excited about him."

Young's rookie season never quite got on track. A pre-draft car accident might have contributed to him being available at No. 17 and he missed all of summer league due to lingering head and neck injuries. In his preseason debut, Young tweaked his hamstring and missed most of the exhibition season. A shoulder injury and a bout with the flu deterred chances for playing time during the regular season and Young ultimately spent much of the year pingponging from Massachusetts to Maine while on assignment with the Red Claws of the D-League.

Young put up some shiny offensive numbers in Maine and showcased his pure abilities as a spot-up shooter (he shot 44.2 percent from beyond the arc in Maine). Even as he worked to improve his defense and diversify his offensive portfolio, the Celtics were comfortable with his progress, having previously determined that he would likely need a year of development before he was truly ready for an NBA role.

But that doesn't make a stream of DNPs any easier for a teenager to endure.

"I feel like traveling from the D-League and coming back and forth, I would always think about, like, 'This is my time. I can do something.' Then I wouldn't get in and then get sent to the D-League again," Young said of a rookie season that featured 11 assignments and recalls. "I think, mentally, that hurt me a little bit. It was all for the best of me. Just keep getting better and using everything that I had. I knew it was a process, like everybody keeps saying."

But while fellow first-round pick Marcus Smart, the No. 6 overall pick, elevated to a starting role in the second half of the year and helped fuel Boston's playoff push, Young watched trade-deadline acquisition Luigi Datome wrestle away any minutes he had previously garnered. Excluding a 24-minute appearance in the regular-season finale, Young played a mere 20 minutes over Boston's final 26 games of the season.

Stevens explained after the season that Young was in a tough spot, unable to get on-court validation for the improvement he was making behind the scenes. He was offensively dominant at times on assignment in Maine. Enough so that Delaware 87ers coach Kevin Young told the Portland Press Herald: "I don't know what Danny Ainge and Coach Stevens are seeing, but that guy should be getting minutes for the Celtics. Unless he just had his best games of his life against us. This is my eighth year in the D-League and I've seen a lot of assignment players come through. He's got to be the best one I've seen. A guy with that size and that shooting ability, he's tough."

"James [Young] has some stuff that you can't teach. And I think James' upside is huge. Like, I'm excited about it. I'm really excited about it." Brad Stevens

But things simply never lined up for Young. The coaching staff and front office assured him he was making necessary progress, but as Boston made a playoff surge, he was a spectator.

"Sometimes you haven't had many opportunities or you're coming back from an injury and all of a sudden you have to play against Avery [Bradley] or Marcus [Smart] or Jae Crowder or Evan [Turner], and just from a physical nature, those guys are older and more physically mature than James," explained Stevens. "But James has some stuff that you can't teach. And I think James' upside is huge. Like, I'm excited about it. I'm really excited about it."

This is a sentiment echoed throughout the Celtics organization. They subscribe to the belief that Young would be a lottery pick this year -- likely inside the top 10 -- if he had stayed for his sophomore season at Kentucky (and, for his part, Young is certain the Wildcats would have won a national title if he had stuck around).

Young is still unbelievably, well, young. He won't turn 20 until Aug. 16. The second-youngest player in last year's draft, Young would still be the 16th-youngest player in this year's draft.

Said Stevens: "You have to keep that in mind. We've had draft workouts here with guys who are two and a half or three years older [than Young], and that's something that you kinda take a step back and think, 'Whoa.'"

Young is almost exclusively focused on summer league and the chance to show his improvements when the Celtics compete in both the Utah Jazz and Las Vegas summer leagues. Ask him if he's planning on taking any time off this summer, he pauses as if he had not previously considered the notion.

"Nothing yet," he shrugged.

But his eyes widen at the mere mention of summer league.

"You don't even know," Young said. "I just want to go out there and just play my heart out. I want to treat summer league like it's the season, and just go out there and play. Me and a couple guys have been in here grinding since the season has been done with and we can't wait to just show our talents."

Echoed Stevens: "That's one of the reasons I think he's around. He's eager. He's really excited. It is so hard -- you get down, and I don't care who you are, I don't care about how positive you are, I don't care about how much of a cheerleader you look like to everyone else, it's hard [not to play]. But after the season, inevitably, if you have another season left, there's like this breath of fresh air, and everything is anew. That's the way he's really looked. I'm excited about that."

Neither the team nor Young have set expectations for next season. Elevating to a rotation role seems the minimum, but given his offensive skill set, it's not unreasonable to wonder if Young is capable of a bigger sophomore leap, especially considering Boston's need for offense, especially 3-point shooting.

It's on Young to force the issue. The team is confident he can be a capable defender, but he must improve his footwork to stick with 2s and use that new bulk to manage 3s. Young said he'd like to be more aggressive offensively, attacking the basket more, and is working on going to his right more often.

Boston is hoping to add more talent this summer, both in free agency and the draft, where many mocks wonder if the Celtics will choose shooting if they stick at No. 16. Young seems ready to fight for his role. He's eager to show his improvements. He wants to eliminate the question marks from all those blog headlines and make sure no one questions his work ethic.

Which is why he apologizes for having no big activities planned when asked about his plans for the foreseeable future.

"I'll be here," he said. "And just grinding."