"On the days Josh is pitching, we really feel like we have a chance to win," Bay said. "You feel like on some days it might take only one run, or two."
Bay and Lowell gave Beckett all the runs he needed, giving Boston a 3-0 lead after three innings. Bay hit a two-run shot in the third after Lowell's solo homer in the second.
"When Jason gets hot, as you can see, it's not just singles," Boston manager Terry Francona said. "He starts driving the ball all over the park and, boy, what a different team we look like."
The Red Sox won their third in a row and sent AL Central-leading Detroit to its fourth loss in five games. Boston has won seven straight against the Tigers.
Beckett continually got ahead with first-pitch strikes, which bothered Detroit manager Jim Leyland.
"It makes it easy for him," Leyland said. "That's the only thing I didn't like. I know how good he is. I know it's not easy, but when you get a guy like him you know he's going to come after you."
There wasn't any carry-over from Tuesday night's bench-clearing brawl that began when Red Sox star Kevin Youkilis was hit by a pitch from Rick Porcello and charged the mound. Both players were suspended five games -- Porcello appealed the penalty, Youkilis didn't.
"It's been nice being home and getting those timely hits," Beckett said of the first three games.
Emergency starter Zach Miner (5-3), who also took the loss in relief in Monday's series opener, gave up five runs and seven hits in 4 2/3 innings. Scheduled starter Armando Galarraga was scratched with severe sore throat.
Beckett had pitched 18 scoreless innings before Guillen's homer on the first pitch of the fifth, which was the Tigers' initial hit of the game. Beckett recorded consecutive seven-inning shutout efforts in his previous two starts.
"He was good," Thames said of Beckett. "He was mixing his pitches up and had us off-balance. We could never get anything going. It was just one of those nights, he put it on us."
Boston had scored a total of two runs in three games before returning to Fenway Park this week. The Red Sox have hit eight homers in the first three games of the series.
Lowell's homer was his third in two games after he entered Tuesday as a pinch-runner when Youkilis was ejected and hit a pair of homers.
Bay has four homers in five games, raising his season total to 24.
The Red Sox broke it open with a five-run fifth. Lowell and Casey Kotchman had RBI singles and Jason Varitek drew a bases-loaded walk. The other two runs scored on a passed ball by Alex Avila and a throwing error by third baseman Brandon Inge.
Detroit's Miguel Cabrera, who left Tuesday's game after getting hit on the left hand, didn't play. ... Popular Red Sox TV announcer Jerry Remy, who took an indefinite leave of absence following complications from cancer surgery, said he is suffering from depression and that the condition has delayed his return to the booth. He was given a standing ovation when he was shown on the center field scoreboard in his first visit to the booth since his leave. ... The Tigers held a closed-door team meeting before batting practice. ... Detroit recalled RHP Freddy Dolsi from Triple-A Toledo. RHP Chris Lambert, who took the loss Tuesday, was optioned to Toledo. Dolsi got some work, giving up three runs -- one earned -- in 1 1/3 innings. ... Galarraga is expected to start Sunday against Kansas City.