Mets starter Zack Wheeler gave up only one run in...

Mets starter Zack Wheeler gave up only one run in seven innings but took the loss in a 7-0 decision to the Giants on Friday in San Francisco.   Credit: AP/D. Ross Cameron

SAN FRANCISCO — On the eve of another lost September, the Mets’ 7-0 loss to the Giants on Friday night had all the hallmarks of their season: great starting pitching, minimal hitting and no relief from the bullpen.

The game was close until the eighth, when Robert Gsellman, Daniel Zamora and Drew Smith allowed two runs each. “When you make mistakes, big-league hitters will make you pay,” Mickey Callaway said of his young relievers. “We’ve been making a lot of mistakes lately.”

Zack Wheeler allowed one run in seven innings, striking out nine and walking none. The only run came in the seventh on a sacrifice fly by Chris Shaw, 24, making his major-league debut and playing in place of Andrew McCutchen, who was traded to the Yankees on Friday.

Wheeler said part of his recent increased effectiveness is throwing his slider as a “strike-to-ball” slider, as Callaway calls it.

“It really starts with me just trusting it,” Wheeler said. “Usually, if I try to start it outside corner and let it run off, it’s going to be a ball every single time. When you start it more as a strike and fade it off, it looks more like a strike coming in so it’s going to be more effective.

"I’ve really been working with [Devin Mesoraco and Kevin Plawecki] back there. They drill in me, ‘Throw it right down the middle and really let it work.’ So that’s really what I’ve been doing.”

In eight starts since the All-Star break, Wheeler has a 1.19 ERA, second best in the majors behind Pittsburgh’s Trevor Williams (0.84). Cy Young Award candidate Jacob deGrom in the same span: 1.69.

It was fitting, then, that the Mets’ lineup treated Wheeler to the deGrom special: no run support. Rookie lefthander Andrew Suarez allowed three baserunners — including Jeff McNeil twice, on a double and a hit-by-pitch — in seven innings to lower his ERA to 4.19.

The Mets have a .227/.303/.350 slash line against lefties. “It’s concerning,” Callaway said.

Meanwhile, Peter Alonso, the righthanded-hitting first-base prospect they will not call up in September, went 4-for-5 with two homers, four RBIs and four runs for Triple-A Las Vegas. He has 35 homers and 117 RBIs.

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