Chris Bassitt had his shortest start in three months, failing to get through the fourth inning as the NL East-leading New York Mets lost to the Chicago Cubs 5-2 Monday night.
New York remained 1 1/2 games ahead of Atlanta, which lost 3-2 in San Francisco.
The Mets had won each of Bassitt's last eight starts, a span in which he had a 2.24 ERA. But the right-hander gave up five runs in 3 2/3 innings - his quickest exit since he lasted a season-low 3 1/3 innings against San Diego on July 8.
Rafael Ortega homered in the second - the first home run allowed by Bassitt (13-8) since he gave up Manny Machado's round-tripper July 23, a stretch of 54 1/3 innings. Zach McKinstry hit a two-run shot in the third before Ortega and Alfonso Rivas each had an RBI single in the fourth.
A quartet of relievers blanked the Cubs on two hits over the final 5 1/3 innings. But the Mets stranded 10 runners - including seven over the first six innings against rookie right-hander Javier Assad (1-1), who allowed five hits in earning the first victory of his career.
Mark Canha struck out with the bases loaded in the first. James McCann delivered a two-out RBI single in the fourth, when Brandon Nimmo whiffed to leave two on. Eduardo Escobar tripled with two outs in the sixth but was left there when Assad struck out Tyler Naquin.
The Mets loaded the bases with none out but didn't score in the eighth when Showalter utilized Mychal Givens - who'd pitched the seventh and eighth - as a pinch-runner at first base for designated hitter Daniel Vogelbach. It was the first pinch-running appearance of Givens' eight-year career.
But Manuel Rodriguez struck out Canha before giving way to Brandon Hughes, who retired Escobar and pinch-hitter Darin Ruf on flyouts.
Hughes gave up a two-out homer to Francisco Lindor in the ninth before retiring Jeff McNeil on a groundout for his fifth save.
Escobar, who also singled in the fourth, extended his hitting streak to 10 games. He's batting .500 (18 for 36) during the run.
Adrian Sampson (1-5, 3.76 ERA) has one win in 14 starts this season despite allowing two runs or fewer nine times, including in each of his last three outings.
Mets: RHP Jacob deGrom (5-1, 1.66 ERA) has retired at least 12 consecutive batters in each of his last six starts, the longest such streak in the last 40 years.