BALTIMORE — The Boston Red Sox maintained a share of the AL wild-card lead tonight, using four home runs to beat the Baltimore Orioles 8-7 and set up a dramatic conclusion to the regular season.

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Ryan Lavarnway, who spent parts of the last two seasons with the Portland Sea Dogs, walks away from home with teammates David Ortiz and Adrian Gonzalez after hitting a three-run homer tonight in the fourth inning at Baltimore. He later added a solo homer in Boston's 8-7 win. ASSOCIATED PRESS

The skidding Red Sox were 6-19 in September before rebounding to edge the last-place Orioles. The win, combined with Tampa Bay’s 5-3 victory over the New York Yankees, kept Boston and the Rays tied with one game left.

After blowing a nine-game lead in the span of 23 days, the Red Sox will send Jon Lester (15-9) to the mound against Baltimore on Wednesday night in an effort to get into the postseason for the fourth time in five years. Lester, Boston’s winningest pitcher, will be throwing on three days’ rest.

Boston will be looking to put together its first winning streak since sweeping a doubleheader from Oakland on Aug. 27. If the Rays and Red Sox remain tied after Wednesday, Tampa Bay will host a one-game playoff Thursday.

Rookie Ryan Lavarnway, who spent parts of the last two seasons with the Portland Sea Dogs, became the unlikeliest of heroes for Boston, hitting his first two major league homers after being thrust into the lineup because of injuries to catchers Jarrod Saltalamacchia (sore collarbone) and Jason Varitek (knee).

Lavarnway, a Yale philosophy major who never played a big league game before August, hit a three-run drive in the fourth inning and added a solo shot for an 8-4 lead in the eighth.

Jacoby Ellsbury and Marco Scutaro also connected for Boston, which scored all its runs on home runs.

Alfredo Aceves (10-2) pitched 3 2/3 innings of three-hit relief for the Red Sox, who survived homers from Baltimore’s Matt Wieters and Adam Jones.

After the Orioles scored twice in the eighth off Daniel Bard to make it 8-6, Jonathan Papelbon survived a hectic ninth for his 31st save. Wieters drove in a run with a grounder and Baltimore had the potential tying run at second with two outs before Jones grounded out on a 3-2 pitch.

Pitching at Camden Yards for the first time since being traded by Baltimore to Seattle in February 2008, Boston starter Erik Bedard gave up three runs and five hits in 3 1/3 innings. The left-hander struck out six but needed 84 pitches to get 10 outs.

Bedard retired the first two batters without difficulty, then walked Nick Markakis and yielded an RBI double to Vladimir Guerrero to fall behind 1-0.

Boston took the lead in the third against rookie Zach Britton (11-11) when Scutaro hit a two-out double and Ellsbury followed with his 32nd homer. Ellsbury has hit in 35 straight games against the Orioles, a streak that began on April 17, 2009.

Lavarnway connected on a 3-2 pitch in the fourth following singles by David Ortiz and Adrian Gonzalez. Wieters answered in the bottom half with his 22nd home run, the second in two nights, to make it 5-3.

A triple by Carl Crawford and Scutaro’s homer off Jason Berken made it 7-3 in the sixth. Jones led off the bottom half with a homer off Aceves.

NOTES: Boston’s Jed Lowrie started in the cleanup spot for the first time in his career. He went 0 for 5 with two strikeouts. … Saltalamacchia was available if needed. Before the game he said, “I feel good, I feel like I can perform, but if it takes today to be 100 percent tomorrow, then that’s what we’ll do.” … Boston Manager Terry Francona said RHP Clay Buchholz, who’s on the 60-day DL with a back strain, could find his way onto the postseason roster. … Boston starters have a 7.28 ERA in September.