NEW YORK -- The New York Mets are looking forward to seeing Jeff McNeil over the final five-plus weeks of the season. The San Francisco Giants are beginning to steel themselves for the likelihood that Wednesday could be one of the last times they see Buster Posey before Opening Day 2019.

McNeil will look to continue his dream season Wednesday night, when the Mets host the Giants and Posey in the third game of a four-game series at Citi Field.

McNeil tied a career high with four hits Tuesday night, when he laced the go-ahead RBI double in the eighth inning of the Mets' 6-3 victory.

The Mets' Noah Syndergaard (8-3, 3.40 ERA) is scheduled to face the Giants' Casey Kelly (0-1, 1.69) on Wednesday in a battle of right-handers.

Kelly gets a task that has befuddled most pitchers thus far: How to get out McNeil, a 26-year-old rookie who entered this season with 18 games above Double-A and nine homers in 1,274 professional at-bats.

But McNeil surged on to the radar by hitting a combined .342 with 19 homers and 71 RBIs in 88 games between Double-A Binghamton and Triple-A Las Vegas. The rebuilding Mets (55-70) finally promoted him July 24, and all McNeil has done since then is hit .326 with two homers and nine RBIs while becoming the first player in team history to collect two four-hit games in his first 27 contests.

McNeil has been particularly hot over the last six games, during which he is 12-for-23 with four extra-base hits and only four strikeouts. Manager Mickey Callaway, a former pitching coach, said he has been impressed with how McNeil has already adjusted to the book getting out on him by mixing up his approach at the plate.

"It's hard to adjust to a guy that can kind of cover multiple pitches and multiple zones and then locations -- it's really tough," Callaway said Tuesday night. "Their pattern has been random already, it seems. It's not like they're trying to attack him with fastballs up and in and bury them in the dirt. I think they have been moving the ball all around. They just haven't figured him out because he's hard to figure out because he can barrel up a lot of different pitches.

"As a pitcher, they're just scrappy little guys and you hate facing them."

Pitchers may not be facing Posey for much longer. The San Francisco Chronicle reported during Tuesday's game that the perennial All-Star and former National League MVP will likely undergo surgery soon to repair a labrum injury and bone spurs in his right hip.

Posey, who did not play Tuesday but is expected to start Wednesday, said following the game he has known for months he would need surgery but that he hasn't yet decided when he'll undergo the procedure. He said he plans to have surgery early enough so that he can return for the start of next season.

"Just talking with doctors and stuff, I think the goal will be to be ready day one, on the opener," Posey said.

Posey is batting .286 with five homers and 40 RBIs in 103 games this year for the Giants (62-65).

"Sometimes it comes to a point where you have to do something about it," Bochy said. "And that's what we're talking about now."

Syndergaard took the loss in his most recent start Friday, when he allowed four runs over 5 2/3 innings as the Mets fell to the Philadelphia Phillies 4-2. Kelly made his first big league start in more than two years Friday, when he allowed one run over 4 1/3 innings and didn't factor into the decision in the Giants' 2-1, 11-inning loss to the Cincinnati Reds.

Syndergaard is 1-2 with a 3.66 ERA in three regular-season starts against the Giants. He will be facing San Francisco for the first time since the National League wild-card game Oct. 5, 2016, when he tossed seven scoreless innings of two-hit ball and struck out 10 but didn't factor into the decision as New York lost 3-0.

Kelly allowed one run over three innings of relief in his lone appearance against the Mets on April 22, 2016, when he was a member of the Atlanta Braves.