Peralta, obtained from the Cleveland Indians on Wednesday, hit a solo homer in his first at-bat in the second inning then connected again off Jon Lester, a two-run shot in the fifth.
"It's something special, this first at-bat for the Tigers," Peralta said. "I feel good to come here the first game and do what I'm doing"
Going into the game, Peralta had just two singles in 15 at-bats against Lester with one RBI, five strikeouts and two double plays. On Friday he also walked against Lester and singled off Ramon Ramirez.
"He hadn't had much success with [Lester] but neither have a lot of other guys," Detroit manager Jim Leyland said. "So it was nice to see him get on the board right away as a Tiger."
Detroit took a 6-1 lead into the ninth and Valverde struck out leadoff hitter Eric Patterson. Then he walked the next three batters and Ortiz connected for his 22nd homer, just clearing the low fence in right field.
"It was a nice swing," Boston manager Terry Francona said. "Would have been nicer if it was a five-run homer."
With two outs, Adrian Beltre then doubled and J.D. Drew was walked intentionally. But on his 60th pitch of the game, 12 more than his previous career high, Valverde retired Mike Cameron on a called third strike with a splitter.
"That's a pretty gutsy pitch," Francona said. "I would have been looking for a fastball, too."
The pitcher pounded his right fist on the mound and catcher Gerald Laird punched the air as the ball broke over the plate.
"I just didn't get it done," said Cameron, who struck out in his last three at-bats, twice against Valverde. "One of those rough nights. Threw a good pitch."
The Tigers, just 4-12 since the All-Star break, acquired Peralta for left-hander Giovanni Soto to play third base after Brandon Inge went on the disabled list with a broken left hand. Peralta has nine homers this season, none in his last eight games with Cleveland and two in his last 23.
Armando Galarraga lost a chance for the win when he was struck on the outside of the right ankle by a liner from Kevin Youkilis with two outs in the fifth and Detroit leading 4-1. He left with a bruise and was replaced by Enrique Gonzalez, who got the final out of the inning.
"He was checked out by the doctors and everything is OK from any type of breaking standpoint," Leyland said. "He's sore, limping a little bit, but he should be fine."
Robbie Weinhardt (1-1) was awarded his first career victory after allowing no runs in the next two innings.
The Red Sox lost the opener of a seven-game homestand after sweeping a three-game series against the Los Angeles Angels to end their West Coast swing at 6-4.
Lester (11-6) fell behind quickly and lost his third straight start. Austin Jackson led off the game with a single and scored on a double by Will Rhymes that bounced off the glove of Cameron as he ran to deep left-center field. Peralta's homer to left made it 2-0 in the second.
His second shot over the left-field wall following a single by Miguel Cabrera put the Tigers ahead 4-0.
Marco Scutaro hit his seventh homer of the season for Boston to cut the lead to 4-1 with one out in the fifth. One out later, Youkilis ripped a pitch off Galarraga's ankle and got a single as the ball bounced toward the left-field line. Galarraga went down on the mound and Leyland and a trainer went out to check on him.
After staying on the ground for about five minutes, Galarraga got up and walked slowly to his dugout. Gonzalez then walked Ortiz and threw a wild pitch, putting runners on second and third, then retired Victor Martinez on a long drive to left-center.
Detroit added two runs in the eighth. Tim Wakefield walked Jeff Frazier and allowed a single to Gerald Laird before both runners moved up on a sacrifice by Danny Worth. Frazier scored and Laird took third on a wild pitch, then scored on a groundout.
- At 43 years, 362 days, Wakefield became the oldest pitcher to appear in a game for the Red Sox. He passed Dennis Eckersley, who was 42 years, 358 days.
- LF Johnny Damon was a late scratch for Detroit with pain in the middle of his back.
- Frazier, called up Friday after hitting 23 homers for Toledo (IL) this season, went 0 for 3 with two strikeouts as the DH.
- Boston OF Jacoby Ellsbury, on the DL since May 28 with fractured ribs, is scheduled for a rehab appearance Saturday with Pawtucket (IL).
- Lester allowed four runs and 11 hits in six innings with seven strikeouts and two walks. He has at least six strikeouts in each of his last nine games.