OAKLAND, Calif. -- The Boston Red Sox escaped an enormous jam in the eighth inning Tuesday, but couldn’t do the same in the ninth and hit the midway point in the season with a gut-wrenching 3-2 walk-off loss to the Oakland Athletics.

A’s pinch-hitter Brandon Moss singled home Chris Carter to tie the game in the ninth and Coco Crisp brought home the winning run with a sacrifice fly.

At 42-39, the Red Sox sit 6 1/2 games behind of the first-place New York Yankees with 81 games to go. They’ll play a 4:05 p.m. EST matinee Wednesday before heading home to start a three-day, four-game series with the Yankees on Friday in Boston.

The ninth-inning blown save by Alfredo Aceves spoiled a terrific eighth inning by Vicente Padilla, who pitched around a nearly debilitating error.

Red Sox shortstop Mike Aviles let a line drive by Kurt Suzuki deflect off his glove to lead off the bottom of the eighth. Crisp followed with a single and Jemile Weeks’ sacrifice bunt moved both runners up.

Padilla was ordered to intentionally walk Josh Reddick to load the bases. Then he relied on nothing but gas to record the final two outs.

After falling behind 2-0 to Cuban slugger Yoenis Cespedes, Padilla fired three straight fastballs. Cespedes fouled off the first, looked at a strike on the second, then swung through strike three for the second out of the inning.

Jonny Gomes followed. He took a pair of heaters for strikes, then couldn’t catch up to a 95 m.p.h. fastball as he struck out swinging to end the inning.

The ninth inning rendered all of that moot.

Carter led off with a single. Brandon Inge popped out and Cliff Pennington singled. Moss, who hit a three-run homer in Monday’s 6-1 Oakland victory, singled up the middle to score Carter. The hit was misplayed by center fielder Ryan Kalish, allowing Moss to move up to second.

Crisp ended it when he hit a high fly ball to Kalish in medium deep center field. The relay throw home wasn’t nearly in time.

Jon Lester had one of his better starts of the season, allowing just one run -- a leadoff homer to Crisp on his third pitch of the game -- over 6 2/3 innings. Lester gave up four hits, struck out nine and walked one.