NEW YORK -- The National League’s leading hitter is back at Citi Field for the stretch run.

The Mets activated Jeff McNeil off the injured list on Saturday, after he missed the minimum 10 games due to a strained left hamstring. McNeil was not in the starting lineup for Saturday night’s 9-5 loss to the Braves against left-hander Max Fried, but he came off the bench in the seventh as a pinch-hitter, and doubled. He stayed in the game at second base, and singled in the ninth. McNeil will start Sunday versus another lefty, Dallas Keuchel.

“I was really happy how the recovery went,” said McNeil before the game. He entered Saturday’s play leading the National League with a .332 average, and raised that to .336 with his two hits. “I’m just ready to get back out there.”

To make room for McNeil on the active roster, the Mets designated outfielder Aaron Altherr, who was batting .082 in 49 big league games this season, for assignment. McNeil will start at second base on Sunday, but is also likely see time at third base and both corner-outfield spots. His presence should result in small playing time reductions for J.D. Davis, Juan Lagares, Joe Panik and Todd Frazier, rather than a significant dip for any one of those players.

For manager Mickey Callaway, a more difficult decision may be where McNeil hits in the lineup. Although McNeil was the Mets’ unquestioned leadoff hitter prior to his injury, Amed Rosario thrived in that role in his absence, batting .419/.457/.558 in nine games as the leadoff hitter. Callaway indicated that he may consider batting Rosario first and McNeil second now that both are in the same lineup again.

“That’s a tough one,” Callaway said. “We’re going to have to think about that. I’ve been thinking about it all day when I found out that we’d probably be activating him and he’d be playing second base. So I’m not quite sure. We’ll have to see what happens.”

No matter where McNeil hits, he offers the Mets the promise of elite contact skills. McNeil has led the NL batting race for large swaths of this season, and is hitting .332/.400/.529 overall with 15 home runs in 105 games.

“It’ll be fun,” McNeil said of his batting title chase against Christian Yelich, Bryan Reynolds and others. “Right now, I’m just glad to be back on the field. Hopefully, I’ll keep swinging the bat well, and hopefully, we can keep getting wins. The ultimate goal is to get back in the playoffs.”

Catcher swap

A day after taking a Josh Donaldson backswing off his helmet, Mets catcher Tomas Nido landed on Major League Baseball’s seven-day injured list for head injuries. Team doctors diagnosed Nido with a concussion.

To replace him, the Mets called up veteran catcher Rene Rivera, who was batting .254 with 25 home runs and an .820 OPS at Triple-A Syracuse. The Mets signed Rivera this spring after another veteran, Devin Mesoraco, declined to report to Syracuse when he did not make the team.

A strong defender and pitch framer, Rivera is popular with Mets teammates who played alongside him in Flushing from 2016-17. After the Mets fell out of contention in ’17, they allowed the Cubs to claim Rivera off waivers, giving him a chance to play in the postseason. He bounced from Chicago to Los Angeles and Atlanta last season, before signing back with the Mets on a Minor League deal this spring.

Rivera’s playing time in Flushing is likely to be sparing, given how heavily the Mets have relied on starting catcher Wilson Ramos since the All-Star break. He nonetheless gives the team a proven veteran option in Nido’s absence. Likewise known more for his defense than offense, Nido was batting .207 with three home runs and a .567 OPS in 39 games.