The duo will join Al Reyes, Dan Wheeler, Gary Glover, Scott Dohmann and J.P. Howell to round out a bullpen with an impressive pedigree.
Percival and Miller alone have combined for over 1,000 Major League innings, and Wheeler, who was acquired from Houston midway through 2007, was with the Astros during their World Series run in 2005.
Each pitcher has persevered through injuries, slumps, and in Percival's case, near-retirement. Their styles are different, but their mantra is the same: to resuscitate the Rays from the American League East cellar.
"Almost every [bullpen] that I played in, I try to instill one thing: We're going to be guys who are going to take the ball everyday regardless of what's happened the day before," Percival said. "We've got that group here; we've got a lot of resilient guys, guys who've been around a long time."
While the average age of the bullpen is 32, the veterans have seamlessly folded into the locker room mix of daily pranks and witty banter. In fact, they often initiate it.
"I think we work very hard and I stack our work against anyone else's, but what we lacked is that sense of humor," manager Joe Maddon said. "The veterans are saying it's OK to have a good time also, and to lighten it up a bit."
Maddon says Percival, who, at 38, is the club's oldest player, serves as a gauge for the Rays, helping to bridge the gap often created between a young squad and the coaching staff.
"He's in the middle of the whole thing," Maddon said last week, gesturing toward Percival in the midst of the team huddle and daily joke.
"He's made a huge difference and we've needed it sorely and now we've gotten it. Not only [from] him, it's Cliff [Floyd] and Danny Wheeler and Trever Miller. These guys are excellent."
And the admiration is far from being one-sided. With neighboring lockers, Miller has had the pleasure of witnessing Percival's straight shooting techniques firsthand.
"It's been a very interesting spring for me," Miller said.
"He [Percival] can kid with guys and when it's not a joke, pull them aside and say, 'I know we were joking a little bit, but seriously, you really need to work on this'. And he doesn't embarrass them in front of the club. He's always smiling, always got a comment or a joke and he seems to talk to everyone; he doesn't have that clique. ... I love that guy."
But it will take more than clever antics and camaraderie to augment a bullpen that produced baseball's highest ERA in the last half century.
Gone are Shawn Camp, Ruddy Lugo and Brian Stokes, who appeared to be every hitter's dream last season, as opponents averaged .358 against the trio.
"Guys didn't know how to come out and attack hitters, throw strikes," Percival said. "That's what you've got to have. You've got to give yourself an opportunity of not giving up too many free bases."
Miller was equally steadfast in his initial prognosis for the club.
"Hopefully everybody can come and execute their pitches, and be the pitcher that they are, not what happened in the past," he said. "If that happens, we are going to be very solid."
With the addition of Percival as a closer, Reyes can slide into the setup role and help strengthen the Rays down the stretch. The 37-year-old had 26 saves last season for a club that lost 16 games in the final three innings. Miller's left-handedness also adds dimension to a relief corps dominated by righties. Miller boasts a career .238 average against left-handed opponents during stints with six teams, including a previous two-year stay with the Rays, over the past nine seasons.
"It's a great mix of a very young pitching staff, starting rotation, and a veteran bullpen and if you get those lined up, they usually spell success," said Miller.
Going into Monday's season-opener in Baltimore, having the marquee relievers match their previous successes would go a long way in helping the beleaguered Rays franchise reach .500 for the first time in its history.
But, this spring, their presence alone has enabled the club to turn a corner.
Whether it is Percival's playful jokes, Wheeler's World Series stories, or Miller's quiet example, the veterans realize they were signed both to bolster the bullpen and to mentor an incredibly talented group of young players.
And the lessons aren't just for the first and second-year guys.
Percival, who has been out of the AL for three years, says he will draw upon the other six pitchers in the bullpen when facing an unfamiliar hitter.
"I don't want to set personal goals, I don't think any of these guys want to set personal goals," Percival said.
"I think it's more as a bullpen, we want to be in the top five bullpens in the league. We do that, our team's got a chance to do something at the end of the year."
Despite a team-best Spring Training record, the Rays will enter the regular season just like the 29 other teams -- with a clean slate.
Still, that's not to say that all will be forgotten.
When asked about the effect of having proven professionals in this year's camp, Maddon said it has markedly improved team morale.
"I think if you ask any professional organization, of the impact of [having] veteran players to 'police the clubhouse', I think that's true," he said. "When you receive peer pressure in a sense from a respected individual in this profession it always will carry more weight."
And for Maddon and the Rays, becoming a team that believes it can win is something that will never grow old.