"Because we're the best-looking guys on the team, right?" Diaz joshes.
Well, let that be their little secret.
They do have the right look here, though. Because on a Pirates club full of youngsters, Overbay and Diaz are proving there's still room for old Bucs.
"That's really behind some of the moves we made in the offseason," general manager Neal Huntington said. "First off, these players have to perform. And if they perform, there are other things they can bring to our team. They have experienced — either secondhand or firsthand — some of the things we're going through."
Overbay and Diaz, the only players on Pittsburgh's 40-man spring roster who were born in 1979 when the Pirates last won the World Series, both signed as free agents in the winter. Starter Kevin Correia and relievers Jose Veras and Joe Beimel, all in their 30s, also came over.
They're now part of a team that lost a major league-high 105 games last year and has endured 18 straight losing seasons. There's talent on the way, however, with the likes of Andrew McCutchen, Pedro Alvarez, Neil Walker and Jose Tabata forming an emerging nucleus of talent, all of them 25 and under.
Overbay is heading into his 11th season in the bigs, having played with the likes of Vernon Wells, Roy Halladay, Troy Glaus, Frank Thomas and other All-Stars in Toronto. He realizes the Pirates want his veteran presence.
"Young guys can get caught up in the life," the 34-year-old Overbay said, adding that he wasn't singling out any of his new teammates. "You can lose sight of what's most important. It's not just being in the big leagues, it's staying here.
"I was young, too. There were times when I didn't eat the best," he said. "The life catches up to you. You have to be ready to answer the bell because it's going to be rung."
Diaz reached the playoffs last October, under the steady hand of Braves manager Bobby Cox. At 33, Diaz played alongside Chipper Jones, John Smoltz, Tim Hudson and others in Atlanta and learned what makes a major leaguer a true major leaguer.
Diaz is trying to share his knowledge with the Pirates. He's been friends with McCutchen since the center fielder was a freshman in Florida, and is getting to know Walker, the promising second baseman.
In particular, Diaz wants to teach Walker one big word: "No."
"Neil is a real nice person and wants to please everyone," Diaz said. "Autographs and appearances and everything. But you can't always say yes to everyone. You have to draw the line, so that you don't let things interfere with your preparation and your game."
Overbay has taken a special interest in Alvarez, who made his major league in mid-June and hit 16 home runs.
"We've talked some about hitting," Overbay said. "I'm not the kind of guy who's going to walk up to someone and just give them my opinion. I think it's more in how you go about your business, that's what people notice."
The 24-year-old McCutchen is one of the bright stars in the game. He hit 16 homers and stole 33 bases last season and big things are projected for his future. He appreciates what players such as Overbay and Diaz bring, on and off the field.
"It's always good to have veterans like that," McCutchen said. "A bunch of young guys like us, you need that."
"It's the small things they can teach us," he said. "They have been where we want to go, they've done what we want to do."
Veras and Beimel might bring that kind of stature to the bullpen. The Pirates had a majors-worst 5.00 ERA last season and could benefit from a pair of relievers who have pitched in the playoffs. Both signed minor league deals with Pittsburgh in the offseason.
Veras spent parts of four seasons with the New York Yankees, where winning was expected.
"He's got presence out there," new manager Clint Hurdle said.
Diaz begins this season as a platoon right fielder, sharing the spot with Garrett Jones. Whether he's on the field a lot or not, Diaz is certain his pal Overbay and the other vets will help steer these Pirates.
"We'll always have a voice," he said.