ST. PETERSBURG -- Two new jerseys hung in the Rays' clubhouse prior to Tuesday night's game against the Yankees, as the first wave of callups -- catcher John Jaso and outfielder Fernando Perez -- arrived earlier in the afternoon and were given warm welcomes by their first-place teammates.

The addition of the two should help bolster the Rays' bench and give always-scheming manager Joe Maddon more options in the regular season's final month.

Perez will likely fit in as a potential pinch-runner, although Maddon said he "wouldn't hesitate" to put the speedy outfielder in a game as a defensive replacement at the outfield corners.

"You always really have to be cognizant in games in which you are losing by a lot or winning by a lot in getting people off their feet," Maddon said. "If we have to make a move within a game, [Perez] defensively is kind of an attractive situation."

Although the Rays' skipper said that center fielder B.J. Upton "isn't going anywhere," Maddon didn't rule out inserting Perez to give Upton a day off at some point down the stretch. Perez batted .288 with 43 stolen bases and 86 runs scored at Triple-A Durham this year, and although he was Durham's center fielder, Perez was confident in his play in the outfield corners.

While Jaso admitted he was "caught way off guard" with the news over the weekend, Perez, who didn't play in two Durham games prior to the move, said he knew something was up.

"I felt it was a possibility all year," Perez said.

But actually getting the nod to help the Rays, who are in the middle of a franchise-first pennant race, is another story.

"It's really interesting," Perez said. "It makes it feel like it's not just a 40-man formality. You are actually somewhat needed to plug a hole or play a role, which I am very, very excited to do."

Jaso, a backstop who split time at both Double-A Montgomery and Durham, will serve as the Rays' third catcher and should help ease Maddon's mind should the club need to pinch-run or substitute for starting catcher Dioner Navarro.

While backup catcher Shawn Riggans would likely enter the game behind the plate, Maddon didn't want to "go naked" at the position on the bench. Navarro has also recently been slowed by soreness in both of his hamstrings -- having exited midway through a game on Aug. 26 game -- and Riggans had started five of the Rays' past six games entering Tuesday.

Jaso batted a combined .273 in the Minor Leagues, with 12 home runs and 67 RBIs.

"I was in Double-A most of the year, so I wasn't really thinking that I'd be in this position right now," Jaso said, smiling. "After I got to Triple-A and started hearing all the talk [about the Rays], I realized how good it was that we were winning up here."

And now?

"This is unbelievable," Jaso said.