"Mature for his age" doesn't begin to describe Marcus Martin.
A year ago, the San Francisco 49ers rookie offensive lineman was the youngest player in the NFL.
Born on Nov. 29, 1993, Martin made his first career start (Week 9 against the St. Louis Rams) at just 20 years old.
That came a few years after he started as a freshman at Southern California at 17 years old.
But when talking about a player who has always been ahead of the curve, it's easy to forget that he is still growing. And that's the case for Martin, who feels like he hasn't yet stratched the surface of his potential.
"Man, I have plenty of room to grow," Martin said. "A lot of people tell me that I don't have my grown man strength yet. I laugh at it but it's for real."
Martin was thrust into the starting lineup last fall after starting center Daniel Kilgore suffered a broken leg. The timing of Kilgore's season-ending injury aligned perfectly with Martin's rehab from a dislocated knee cap he sustained during the preseason.
The rookie third-round pick started eight of the remaining nine games, filling in admirably at one of the most mentally demanding positions on the field.
"It was unbelievable," Martin said. "Everything was uphill at first, but I gathered information and by the end of the year, I felt so fluid.
"Playing in real games makes a difference. You actually understand what an NFL game feels like; the type of players you go against. You understand the speed that you have to play with and how quick you have to make decisions."
What makes Martin's rookie campaign even more impressive is the fact that he never felt completely healthy. The knee injury lingered even after he gained the starting center job.
"Looking back, I feel like there were things I could've done better to manage that injury," Martin said. "But now that I'm 100 percent, I'm working on trying to deal with the different impacts on my knee.
"Just getting adjusted to my second year and not looking at things like I'm a rookie. I think the biggest adjustment is just the ownership and the responsibility."
Martin's most noticeable transformation this offseason occurred in the weight room. During OTAs and minicamp, Martin appeared far leaner than as a rookie. He credited the change to the longest-tenured player on the 49ers roster.
"I'm lucky to have a guy like Vernon Davis in my life to be an inspiration and give me motivation," Martin said. "He taught me a lot of things this offseason. One thing I learned from him is that you can't get any better in your career without hard work."
Martin's relationship with Davis began early on in 2014 and evolved as the season progressed.
"I wouldn't say he took my under his wing from the beginning, but he liked me," Martin said. "And when he got to see me play, he was like, 'You know, I really see you having a bright future in the NFL. Trust me, if you put in the work and the time that it takes, you'll be unbelievable.'
"Vernon was a first-round pick but nothing was handed for him. He had to work for it. He fought his battles. So hearing that from a guy who has been doing it for 10 years is phenomenal, man. It's very motivating."
Just days away from training camp beginning, Martin enters as a realistic option to start at three different positions along the offensive line (right guard, left guard and center). The 21-year-old said that he isn't worried about the upcoming competition. This is just the next step in a budding career defined by early success.
"I'm going to play to the best of my abilities. I can't allow the thought of another man distract me from my goals. I have to stay focused," Martin said. "I'm using everything that I learned from an in-game experience and applying it to practice. So when I get my opportunity this year, I'll dominate."