Next up, a key series against the Boston Red Sox.
Pena hit his AL-best 38th homer and drove in four runs to help the Rays beat the Detroit Tigers 11-7 on Monday for a split of their four-game series.
Tampa Bay scored six times in the first inning against the AL Central leaders, capped by Pena's two-run drive. James Shields remained unbeaten against Detroit, and Jason Bartlett added a solo homer as the Rays moved within five games of idle Boston in the wild-card race.
Tampa Bay hosts the Red Sox on Tuesday night, the start of a three-game set.
"I don't know if it gets any bigger," Evan Longoria said. "Today is a great way to head home. It should be fun."
Tampa Bay is 4-1 against the Red Sox at Tropicana Field this season and has won seven of the first 11 meetings.
Carlos Guillen had four hits for Detroit, including a pair of two-run homers.
"It was great," said Pena, who finished August with 12 homers and had his seventh game this season with four or more RBIs. "That first inning really put momentum on our side."
Pena added an RBI double in the fifth and Bartlett homered in the sixth off Washburn, who lost for the second time since joining the Tigers in a July 31 trade with Seattle. He left the mound to a chorus of boos after allowing eight runs and nine hits in 5 2/3 innings.
"He certainly didn't have very good success today," Detroit manager Jim Leyland said. "Some of it by his own doing and some of it was that's just the way it is sometimes.
"Sometimes it just isn't your day."
Pena singled in the first of three Tampa Bay runs off reliever Ryan Perry in the seventh and finished a seven-game road trip with four homers and 12 RBIs.
"Carlos is looking extremely sharp," Rays manager Joe Maddon said.
Shields (9-10) allowed both two-run homers by Guillen, one in the first and another in the seventh, but had little trouble in between. The right-hander yielded four earned runs in seven innings and struck out six to win his second consecutive outing and improve to 3-0 in five career starts against the Tigers.
Guillen had his sixth career multihomer game. Detroit got its last two runs in the ninth off reliever Brian Shouse.
"It feels good," Guillen said. "I hit the ball good. I was just trying to stay short and make good contact."
Pena missed his own club record for homers in a month by one. He hit 13 in September 2007. The Rays' 43 August homers set a club mark. ... Longoria scored three times. ... Guillen also had his eighth career four-hit game. ... Tigers RHP Jeremy Bonderman (shoulder) will be activated from an injury rehab assignment Tuesday but will not be used as a starter, Leyland said. With rosters expanding to 40, the club also will promote pitchers Eddie Bonine and Casey Fien, C Dusty Ryan, OF Wilkin Ramirez and SS Brent Dlugach from Triple-A Toledo. ... Tampa Bay RHP Andy Sonnanstine will be recalled Tuesday from Triple-A Durham to start against Boston. The Rays also will call up C Shawn Riggans, OF Fernando Perez and RHP Jeff Bennett.