Mets starting pitcher Zack Wheeler walks to the dugout during...

Mets starting pitcher Zack Wheeler walks to the dugout during the eighth inning against the Tigers at Citi Field on May 26. Credit: Kathleen Malone-Van Dyke

The Mets’ second half begins Friday in Miami against the Marlins, the only team in the National League with a worse record. Here are five questions that will define the Mets’ next two-and-a-half months.

How long will the manager last?

Mets manager Mickey Callaway looks on from the dugout against...

Mets manager Mickey Callaway looks on from the dugout against the Phillies at Citi Field on Sunday. Credit: Kathleen Malone-Van Dyke

Publicly, at least, general manager Brodie Van Wagenen has stuck by manager Mickey Callaway at every low point in a series of them. If getting swept by the Marlins in May, cursing out a reporter in the clubhouse in June and falling 10 games under .500 in July weren’t enough for Van Wagenen and chief operating officer Jeff Wilpon to fire Callaway, what would be?

Since he has lasted this long, Callaway very well could make it through the season, his second with the Mets. The fall would be a different story, though. Team decision-makers spending October looking for a new manager would surprise nobody.

Which awards and milestones will Pete Alonso collect?

Mets first baseman Pete Alonso reacts after hitting during the first...

Mets first baseman Pete Alonso reacts after hitting during the first round of the Home Run Derby on Monday in Cleveland. Credit: AP/Tony Dejak

Pete Alonso’s banner first half concluded Sunday with his 30th — yes, 30th — home run, followed by his Home Run Derby title on Monday. He heads into the second half as the clear favorite for NL Rookie of the Year, though Braves pitcher Mike Soroka (2.42 ERA) also has been very good and Padres shortstop Fernando Tatis Jr., 20, could make a run at the award.

And then there are all sorts of milestones to watch out for. Among them: the Mets’ single-season homer record (41, done by Todd Hundley and Carlos Beltran) and the major-league mark for homers by a rookie (52, done by Aaron Judge).

To reiterate: Alonso — as a rookie — has a very good chance of hitting more home runs than any Mets batter has in a season in the franchise’s 58-season history.

Will Jeff McNeil win a batting title?

Mets leftfielder Jeff McNeil reacts after he hits a two-run single...

Mets leftfielder Jeff McNeil reacts after he hits a two-run single against the Braves during the eighth inning  at Citi Field on June 30. Credit: Kathleen Malone-Van Dyke

A batting-title chase would be a perfect way to cap Jeff McNeil’s incredible ascendance the past year-plus, from little-known minor-leaguer to All-Star, fan favorite and Nathan’s Hot Dog Eating Contest celebrity judge.

McNeil leads the majors with a .349 average. Right behind him in the National League: the Dodgers’ Cody Bellinger (.336), the Rockies’ Charlie Blackmon (.330) and the Brewers’ Christian Yelich (.329).

Whom will the Mets trade?

New York Mets starting pitcher Zack Wheeler delivers against the...

New York Mets starting pitcher Zack Wheeler delivers against the Philadelphia Phillies during the first inning of an MLB baseball game at Citi Field on Sunday, July 7, 2019. Credit: Kathleen Malone-Van Dyke

For a third year in a row, the Mets have positioned themselves as sellers in advance of the July 31 non-waiver trade deadline. Zack Wheeler is the safest bet to be dealt — he is due to be a free agent after this season and has top-of-the-rotation ability, if not matching results this year — and is the Mets’ best shot at getting a noteworthy prospect in return. The Mets have talked about Noah Syndergaard recently with at least a half-dozen teams, a source said, though a deal for him would be more complicated. Todd Frazier and Jason Vargas  also could draw interest.

A more outside-the-box candidate: Wilson Ramos, whose two-year, $19 million contract runs through 2020. Ramos has been losing playing time to backup Tomas Nido lately, so the Mets could steer into that trend and simply move on from Ramos.

Worth noting: Major League Baseball scrapped the August waiver process and Aug. 31 trade deadline. That means there are no trades allowed after July. If a team wants to add one of the Mets’ players — or if the Mets want to trade any — it will need to happen this month.

The past two seasons, the Mets have prioritized saving money over the prospects they got back. One Mets executive recently suggested that won’t be the case this year.

Will the Mets get any pleasant surprises?

Brandon Nimmo of the Mets bats during the first inning against the...

Brandon Nimmo of the Mets bats during the first inning against the Phillies at Citi Field on April 23. Credit: Jim McIsaac

When the Mets were in this spot in 2017, they had a pair of fun, interesting prospects named Amed Rosario and Dominic Smith to call up. Last year, McNeil. This year, there aren’t any new blue-chippers who will be a reason to watch nightly — though lefthander/Long Island native Anthony Kay is a candidate for a late-season look — so it will be up to others to serve as pleasant surprises. Will Brandon Nimmo rebound from his neck injury to return to his electric 2018 form? Will Syndergaard turn his year around (and improve his trade value, if the Mets want to go that route)? Will Jed Lowrie play?

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