Patrick Bailey hit the go-ahead grand slam in the eighth inning Friday night for the visiting San Francisco Giants, who mounted another multi-run late-inning comeback to stun the New York Mets 8-7 in the opener of a three-game series.

J.D. Martinez, Mark Vientos and Pete Alonso hit solo homers to help stake the Mets to a 6-2 lead before the Giants stormed back against Reed Garrett (5-2). Mike Yastrzemski and Marco Luciano opened the inning with singles before Luis Matos popped out and Luciano was forced at second on a grounder by LaMonte Wade Jr.

Thairo Estrada doubled on the next pitch and Matt Chapman worked a seven-pitch walk before Bailey homered on a 2-0 fastball.

Yastrzemski hit what proved to be a key insurance homer in the ninth before the Mets nearly rallied against Camilo Doval in the bottom half.

DJ Stewart led off with a double and moved to third on a groundout by Brett Baty before scoring on Francisco Lindor's single. Alonso followed by hitting a potential double-play ball to shortstop, but the ball glanced off the glove of Luciano for an error.

Pinch runner Tyrone Taylor stole second and Brandon Nimmo was intentionally walked. Martinez struck out before Vientos hit a slow roller to third, where Chapman made a barehanded grab and threw out Vientos by half a step as Wade corralled the throw.

The Giants have won three straight games, all by overcoming deficits of at least four runs.

Doval's ninth save preserved the first big-league win for Nick Avila (1-0), who allowed one run in two innings as the Giants' first reliever. Starter Kyle Harrison allowed five runs (four earned) on six hits and two walks while striking out six over five innings.

Jorge Soler homered in the second while Matos had a run-scoring groundout in the third for San Francisco.

Alonso had two RBIs while Jeff McNeil hit a run-scoring single for the Mets, who have lost four straight and are 6-15 this month. The late-inning comeback cost Christian Scott a chance at his first big-league win after he allowed two runs on two hits and one walk while striking out four over six innings.