DETROIT -- The Chicago White Sox are shuffling their bullpen, and closer-to-be Chris Sale isn't expected to be ready until next week.

They could have used him on the mound Friday night.

Matt Thornton allowed a two-run homer by Jhonny Peralta in the bottom of the ninth inning, which gave the Detroit Tigers a 5-4 victory over Chicago. Sale is moving from the rotation back to the bullpen to take over as closer, but he pitched six innings Tuesday, so Thornton was left to try finishing Friday's game.

Hector Santiago has been Chicago's primary closer this season, but he has a 7.36 ERA.

"With everything going on today, we looked at the way they were lining up and went with Matt," White Sox manager Robin Ventura said.

After Alex Avila's one-out single in the ninth, Peralta ended it with a homer to right-center off Thornton (1-1).

"I threw one bad pitch tonight, and it got hit out of the park," Thornton said. "He fouled off a good pitch and then hammered a bad one. I left it over the plate and he got the barrel on it."

Jose Valverde (2-0) pitched the top of the ninth for the win.

Chicago led 4-2 after Gordon Beckham's tiebreaking two-run shot in the seventh, but Detroit got a run back in the eighth on an RBI single by Miguel Cabrera.

Chicago starter Jake Peavy allowed three runs and seven hits in 7 2/3 innings, but the bullpen couldn't hold the lead for him.

Detroit outfielder Delmon Young was reinstated Friday from the restricted list following a seven-day suspension, but he didn't play. Young was arrested last week and accused of yelling anti-Semitic epithets in New York.

The Tigers didn't need him. Avila hit his fourth homer of the year for Detroit, and Peralta's opposite-field shot -- his first of the season -- gave the Tigers the win.

"It's the best moment you can feel," Peralta said. "The first home run this year -- and walk-off. It's not bad, huh?"

Beckham had three hits for the White Sox.

Detroit rookie Drew Smyly allowed two runs and seven hits in six innings. He struck out seven.

Smyly hadn't allowed more than a run in any of his first four starts, and he had a 2-1 lead after Avila's solo shot in the fourth. But Alexei Ramirez led off the sixth with a triple and scored on Adam Dunn's sacrifice fly to tie it.

Octavio Dotel retired the first two Chicago hitters in the seventh in short order, but Brent Morel beat out a slow grounder for an infield single, and Beckham's second homer of the season made it 4-2.

Peavy, coming off back-to-back complete games, fell four outs short this time. He allowed an RBI single to Cabrera with his 122nd and final pitch, and Thornton came on and got Prince Fielder on a grounder to the mound, with part of the Detroit slugger's broken bat hitting the screen behind the plate.

"I hate that I couldn't get out of that inning, because that would have made it easier for Matt," Peavy said.

The White Sox are moving Sale back to the bullpen next week, but he isn't expected to pitch in this series. So Thornton came back out for the ninth and couldn't get through it.

The Tigers took a 1-0 lead in the second on a sacrifice fly by Ryan Raburn. Chicago answered in the third with an RBI double from Beckham.

Game notes
Detroit RHP Doug Fister is expected to start Monday at Seattle after missing a month with a left side strain. Fister left his first start of the season April 7 in the fourth inning. ... Paul Konerko had two hits, giving him sole possession of fourth place on Chicago's career list with 2,009 -- two more than Eddie Collins. ... Tigers RHP Max Scherzer (1-3) faces Chicago RHP Gavin Floyd (2-3) on Saturday.