ATLANTA — Just when it looks like it cannot get worse for the Mets, it can.  Soon after Jacob deGrom watched his brilliant tight-rope work unravel in the eighth inning Friday night, Jeurys Familia was flexing and stretching his left leg before limping off the field in the Mets’ 2-1 loss to the Braves at Turner Field.  The Mets (36-33) took their third loss in a row and deGrom suffered his first loss in seven starts, but the loss of Familia would be the biggest blow for the Mets yet. The closer said that he felt tightness in his left inner-thigh, near his groin area, while pitching in that disastrous eighth inning.  “I feel something in my leg a little tight, but I am OK,” said Familia, who got the final out of the inning but said he would not have been able to go back out to the mound for the ninth.  “I want the trainer to look at it and then wait and see. They say it’s OK, maybe a little tight. Maybe a day or two days.”  The Mets have taken their share of injury hits this season. David Wright is out indefinitely with a degenerative back condition. Daniel Murphy is tentatively scheduled to come back Tuesday from a strained left quad and the team is easing catcher Travis d’Arnaud back after he missed 46 games with a broken hand.  Their offense has suffered due to those injuries. With Michael Cuddyer’s single bringing home Ruben Tejada in the sixth, the Mets have managed two runs in their last 26 innings. Friday night was the 37th time this season they have scored three runs or fewer, and they dropped to 8-29 in those games.  They have been able to stay in the National League East race — they hold a half-game lead over the Nationals — only with outstanding starting pitching and quality closing by Familia. That formula, however, leaves the Mets pitchers a thin margin for error, or injury.  The Mets’ lack of punch and defensive mistakes cost deGrom. Pitching on his 27th birthday, the lanky righthander shut down the Braves for seven innings. After cruising into the eighth despite the 90-degree weather and heavy humidity, deGrom hung a curveball to Andrelton Simmons, who doubled to lead off the inning. Simmons advanced to third on Eury Perez’s bunt toward third. DeGrom, a former college shortstop, charged and fielded the ball and turned to fire to third, but Tejada had left the base to charge the bunt, too.  “He hit it pretty hard,” deGrom said. “Ruben had to come in, in case I don’t get there. . . . I didn’t have the play there, so I got the out at first.”  Pedro Ciriaco followed with a ground ball to short, but Wilmer Flores hesitated, twice checking Simmons at third base before making the throw to first, where Ciriaco was safe.  “I thought he was going to go on contact,” Flores said of Simmons. “It was my mistake. I just took too long. He held back and I just took too long to throw to first.”  That put deGrom, and Terry Collins, in a jam. With one out and runners on the corners, the manager decided to take out his starter and put in lefthander Sean Gilmartin to face the lefty-hitting Jace Peterson.  “Yeah, it was a lefty-lefty (situation). Jake was at 97 (pitches), it was 90 degrees out there,” Collins said of his rationale. “He hung a slider. . . . I thought it was time.  “If we had gotten Ciriaco out, he would have stayed in and faced the next guy.”  The “next guy,” Peterson, lined a double over center fielder Juan Lagares’ head to drive in the two runs that cost deGrom (7-5) what might have been his fifth straight win. Lagares said he was playing Peterson, a leadoff hitter, in on that play.  All deGrom (7.1 innings, four hits) could do was watch from the dugout.  “Jake was very good,” Collins said. “We’ve gotten some very good pitching, but we are just not scoring runs.”
After dominating through the first seven innings Friday night, Jacob deGrom watched it all slip away quickly in the eighth.