SAN FRANCISCO — Opportunity wasted.

The Mets were sitting pretty after stomping the Giants in consecutive games, but a combination of blah starting pitching and mediocre offensive production over two days conspired to prevent a series victory.

Tylor Megill followed an ugly David Peterson start a day earlier with his own dud, and the Mets never got rolling offensively in a 5-4 to the Giants on Sunday at Oracle Park.

It left the Mets with a series split against a reeling NL West team.

Drew Smith surrendered an RBI double to Mike Yastrzemski in the eighth inning to allow the go-ahead run.

Smith’s walk to Joc Pederson started the rally.

The Mets finished 7-3 on a West Coast trip that included facing the Athletics and Dodgers, but faced a cross-country flight home on a two-game skid.

Megill scuffled through four innings in which he allowed four earned runs on six hits with one walk and two strikeouts.

The right-hander departed after 81 pitches in what was his shortest and least-effective start of the season.

Want to catch a game? The Mets schedule with links to buy tickets can be found here.

Jeff Brigham gave the Mets two innings of shutout relief with four strikeouts before Brooks Raley escaped trouble in the seventh by striking out Michael Conforto after LaMonte Wade Jr. smacked a two-out double.

Pederson, activated from the injured list before the game, stroked an RBI single in the first that put the Mets in a 1-0 hole.

Megill had gotten J.D. Davis to hit into a double play after allowing a leadoff single to Wade Jr. and walk to Conforto before Pederson delivered.

Thairo Estrada’s homer leading off the second extended the Mets’ deficit to 2-0.

The blast was the fourth allowed by Megill in his last three starts.

The Mets ignited a two-out rally in the third to get on the board against Ross Stripling.

After Starling Marte singled, Francisco Lindor slashed an RBI double to left-center, but was left stranded when Pete Alonso was retired.

Conforto dropped a fly ball that gifted the Mets a run in the fourth, when they scored twice to go ahead 3-2.

Stripling loaded the bases with nobody out before Francisco Alvarez struck out and left-hander Taylor Rogers got pinch-hitter Mark Canha to fly to Conforto, whose drop was ruled a sacrifice fly and error.

Brandon Nimmo followed with a sacrifice fly — which otherwise would have been the third out — for the inning’s second run.

Megill slogged through a fourth inning in which he allowed singles to Yastrzemski, Brandon Crawford and Blake Sabol, the last of which drove in a run.

Megill’s error on a pickoff throw to first base allowed Crawford to score, placing the Mets in a 4-3 hole.

Alvarez’s homer in the sixth tied it 4-4.

The homer was Alaverz’s first since his recall from Triple-A Syracuse on April 7.

The rookie catcher doubled his RBI total with one swing.