WALTHAM, Mass. -- Amir Johnson had just finished declaring himself an "old-school" veteran and, as if to prove it, his brow furrowed when asked about being part of a Boston Celtics' starting five that ranks among the NBA leaders in net rating.

"What does that mean?" Johnson asked a reporter after Thursday's practice. Informed it's essentially a metric that details how a lineup performs per 100 possessions and that Boston's starting five of Isaiah Thomas, Avery Bradley, Jae Crowder, Al Horford and Johnson rank fourth in the NBA, among lineups with at least 350 minutes, at plus-10.3, Johnson appeared unmoved.

"You know what, out of my 12-year career, I’ve never been interested in stats. At all," said Johnson, who also happens to lead the Celtics in ESPN's Real Plus/Minus metric, sitting 19th overall in the NBA. "That fact, man, it really doesn’t matter as long as we’re winning games and doing the right things on the floor. That’s pretty much all that really matters to me. I mean, I could score zero points and, if we win, that’s everything to me. I get happy when I set a good screen and get [Thomas] open for a bucket."

"He doesn't seem to mind individual stats; he seems to mind how he impacts the team," Celtics coach Brad Stevens said of Amir Johnson. "We all know how much he means." Andrew D. Bernstein/NBAE via Getty Images

This is Johnson in a nutshell. The 6-foot-9 big man takes more pride in the fact that Boston's starters are 23-7 in the mere 30 games they've played together this season due to injuries. It's Johnson, still only 29 years old after being one of the league's last prep-to-pros players, who leads the Celtics in appearances this season at 71. And while teammates such as Thomas grab the headlines with otherworldly offensive exploits, Johnson is content to play his under-the-radar role for a Boston team that has positioned itself to make a run at the No. 1 seed in the Eastern Conference.

Celtics coach Brad Stevens is quick to note how advanced metrics spotlight Johnson's value.

"I think the numbers reflect what he means when you look at our on/off numbers," said Stevens, referencing how Johnson's basic stat line -- 6.3 points, 4.5 rebounds over 20 minutes per game -- doesn't jump off the page, yet Johnson is tied with Crowder for the best on-court net rating on the team at plus-7.4.

"Before [Johnson] got here, he was like that, with regard to his impact," Stevens added. "Sometimes those things show up in points and rebounds and assists and all that other stuff. And sometimes they don’t. But he doesn’t seem to mind individual stats; he seems to mind how he impacts the team. We all know how much he means."

The jovial Johnson, who playfully calls himself the "Big Dog," sat down with ESPN.com on Thursday to discuss his less-bark more-bite role in Boston, the joys of fatherhood, and Boston's playoff potential this season.

You're not even 30 but you've been in the league over a decade. Do you see yourself as a veteran leader on this team?

Johnson: "I just think I lead by example, with my attitude. I'm very calm. I’m not that vet that has got to yell and scream at you. I’m just the type that might pull you aside, like an old-school person. I talk to guys. I’ve done it to [rookie Jaylen Brown], I’ve done it to [second-year guard] Terry [Rozier], just pull them aside and tell them my 2 cents. They can either take it or not. That’s the type of person I am."

You were a bit of a rock star in Toronto but in Boston you seem to fly under the radar. Didn't you say last season that people around here didn't even notice you in public?

Johnson: "When I first came to Boston I was on a [Segway] rolling around and I’m already tall as it is. For me, just to be rolling through Faneuil Hall on a [Segway] and nobody really knew I was a player. A few people [recognize me now]. Toronto was pretty hectic, though. When I went around the mall, it was like I had crowds. But Boston, everybody is pretty laid back."

How did you develop such a close bond with teammate Jae Crowder?

Johnson: "Our daughters are real good friends. I think when you bring in families, it just kind of brings us closer. Our daughters are pretty much like two peas in a pod. Same age and they just have fun together. I got her going to the school [that Crowder's daughter is] going to, so they have friends. It just brings us a lot closer. It’s family."

You post pictures of your daughter, Amelia, on Instagram frequently. How has being a dad affected you?

Johnson: "It changes your life, man. It really does. It puts everything in perspective for what your doing things for. It’s pretty much not about you any more. It’s about the kids. Everything you do is to set up a future for your kids. And that’s pretty much my mindset now. I’m all about setting up my daughter’s room. Like I’m really more excited about changing my daughter’s room around in the summer or maybe going to Disneyland. That’s pretty much my mindset."

You've got things to do before then, right?

Johnson: "Don’t get it twisted. I’m definitely ready for us to make a playoff run. I think I haven’t been out of the first round since Detroit days, but then I wasn't even playing. I was in a suit behind the bench. Playing-wise, I haven’t been out of the second round, so I’m looking forward to going deep in the playoffs."

What is this team capable of in the postseason?

Johnson: "To be honest, we’re just trying to take it one game at a time and get our consistency up before we even think about playing in the playoffs. Like Coach says, every game matters and we just have to focus on the next game. Once we get our consistency down, I think we’ll be a great team, we’ll have a chance to go far. We’ve got to make sure we take care of the ball. ... We gotta work on our transition defense, that’s a big key. Our rebounding has gotten better, but we just gotta get it all together, man."

Depending on how the seeds shake out, there's a chance you could play both of your former teams (Detroit, Toronto) in the early rounds of the playoffs. Have you thought about that at all?

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Johnson: "It’s tough because, last year we got caught up thinking about where we were going to be placed and we ended up being in a position that we didn’t really want to be in [a four-way tie-breaker forced Boston to open on the road against Atlanta]. Right now, our focus is just on us before we even get caught up in what seed we are and what place we are in. We gotta be prepared for everything."

What have been your impressions of Brad Stevens after two seasons in Boston?

Johnson: "He’s very detailed, man. He watches a ton of film. He knows his stats where ... I’ve never even heard of some of the stats he says. He really has stuff to back up what he's saying. He puts the numbers together somehow. When you have a guy that’s very persistent with what he does, working and watching film, he’s just a guy that's easy to listen to because he [works at it] every single day and he doesn't change."

Your contract expires after the season and the Celtics have a couple young big men stashed overseas. Have you thought about your future beyond this season?

Johnson: "I haven’t thought about it. My summer plan is just like getting my daughter’s room in order and building the play set in the backyard. That’s it. That’s my mindset. I’ll be doing the same things: getting my body right during the summer, being prepared for games. I’m really the type of player that can really just go out there and play with anybody, whether I’m starting the game or coming off the bench, I can give a little bit of something. Hopefully I can come back here and continue what we’ve got going. I was with Toronto for six years and Detroit for four. I’ve been here for two years. I haven't been going team to team, just one-year rides. You see some guys that go to different teams every year. I kind of like to stay in one place for a while."