The Houston Astros’ Travis Shaw hits an RBI single during the seventh inning in Game 5 of the American League Championship Series against the Red Sox on Wednesday in Boston. (AP photo)

BOSTON — Framber Valdez was perfect through four, took a two-hit shutout into the seventh and became the first pitcher in the 2021 postseason to finish eight innings on Wednesday as the Houston Astros beat Boston 9-1 in Game 5 of the AL Championship Series and moved one win from a second straight trip to the World Series.

Yordan Alvarez had three hits and three RBIs for Houston, which can clinch its third pennant in five years with a victory in Game 6 at home on Friday night. The Red Sox need a win to force a deciding seventh game on Saturday.

One day after the Astros scored seven runs to break a ninth-inning tie, they hung another crooked number on the Fenway Park scoreboard, chasing Chris Sale while scoring five runs in the sixth. Alvarez, who homered in the second and singled in the fourth, had a two-run double to break things open.

That was plenty for Valdez, who extended the staff’s shutout streak to 14 straight innings before Rafael Devers homered with one out in the seventh — one of just three hits for Boston. The left-hander departed after retiring the Red Sox in order in the eighth — the longest outing for any starter this postseason.

In all, Valdez gave up one run on three hits, one walk and a hit batter, striking out five. He was also the first opposing pitcher to last eight innings in a postseason start at Fenway since Cleveland’s Charles Nagy went eight in the 1998 Division Series.

Ryne Stanek pitched a perfect ninth while the rest of Houston’s relievers rested. Astros starters had not lasted three innings all series, pitching to a 18.90 ERA in the first four games and giving up 10 homers — including a record three grand slams.

Valdez was not much better, allowing two earned runs in 2 2/3 innings in Game 1.

But he retired the first 12 batters on Wednesday — eight on grounders, four on strikeouts. Devers singled to lead off the fifth, then Valdez bounced the next pitch off J.D. Martinez’s leg. The Astros escaped when Hunter Renfroe grounded into a double play and Alex Verdugo bounced out to first.

Sale started almost as well, allowing just two hits — both to Alvarez — in his first five innings. But he walked Jose Altuve to start the sixth, then Michael Brantley nubbed one toward third. Devers fielded it and made the throw in time but Schwarber dropped it at first; after sliding into second, Altuve popped up and took off for third, which was uncovered.