New regime, new brash attitude, same old disappointment.

For a third straight year, the Mets will begin the second half all but finished in the postseason race, buried this time not so much by injuries as by underwhelming performance.

In his vow to win now and in the future, new general manager Brodie Van Wagenen perhaps crippled both causes with the offseason trade that brought Robinson Cano and Edwin Diaz to the Mets and sent prospects Jarred Kelenic and Justin Dunn to Seattle. Cano and Diaz simply have been brutal — two big factors in the team’s 40-50 first half.

The glass is at least a quarter full because of the top-end talent that has emerged for the Mets. But it’s three-quarters empty because of the bullpen and a starting rotation that hasn’t pitched to expectations.

Brace yourself for the first-half grades.

Pete Alonso

The Mets’ second half will largely be about the rookie first baseman’s exploits. He figures to shatter the franchise’s single-season record for homers in a season (41), shared by Todd Hundley and Carlos Beltran, and should be considered the favorite for NL Rookie of the Year. Alonso, with his 1.006 OPS, has been everything the Mets could have wanted and more. The Mets have their Aaron Judge.

Grade: A+

Jeff McNeil

Jose Reyes is the only Mets player to win the batting title, accomplishing the feat in 2011, but McNeil has a shot to join the fraternity. He will take a .349 batting average into the second half, having silenced concerns about his ability to produce at a consistent major league level. McNeil also has been steady in the outfield after making the switch from second base. He and Alonso have carried the lineup.

Grade: A+

Dominic Smith

He had almost become a forgotten man in the offseason, but Smith’s strong play forced his way onto the roster and then into the starting lineup. Smith’s .939 OPS in 138 at-bats is among the biggest surprises of the season. First base is blocked with Alonso’s emergence, but Smith hasn’t killed the Mets in left field and he could be a block around which to build.

Grade: A–

Jacob deGrom

The reigning NL Cy Young award winner had a mediocre stretch early in the season, but has rebounded into form nicely. The right-hander is tied for second in the NL with 138 strikeouts and ninth in innings with 110. There is still time for him to jump into the Cy Young conversation, but it will take a dominant stretch to potentially catch the likes of Hyun-Jin Ryu, Max Scherzer and Luis Castillo.

Grade: B+

J.D. Davis

Of all of Van Wagenen’s offseason acquisitions, Davis has performed the best. The former Astros infielder has taken to a platoon role, producing against lefties and off the bench. If Todd Frazier is traded before the deadline, it could give Davis opportunities at third base, but defensively he isn’t great.

Grade: B+

Jason Vargas

The veteran lefty has stepped up and helped carry the rotation after a dismal 2018 season. Team officials have allowed Vargas to work deeper into games, after a stretch in which he was regularly lifted in the fifth inning or earlier. He could serve as trade bait.

Grade: B

Seth Lugo

Heading into late June, the right-hander could have been considered All-Star material in the bullpen. But Lugo had three straight implosions that contributed to the disastrous road trip that all but buried the Mets in the playoff race. Lugo has rebounded and remains the team’s best relief option.

Grade: B

Todd Frazier

He missed all of spring training due to an oblique strain and was ineffective upon his return, appearing destined for the bench. Then Frazier started hitting in mid-May and really hasn’t slumped since. Frazier’s .783 OPS is certainly acceptable, and he’s delivered several big hits in the late innings. Now the Mets will look to deal the impending free agent, who could be a nice bench piece for a playoff contender.

Grade: B–

Michael Conforto

There are stretches in which he just disappears, but Conforto still arrived at the break with 16 home runs and an .830 OPS. Even so, it’s become clear that Conforto probably isn’t the perennial All-Star the Mets thought they had in the making a few years ago. Conforto’s recovery from shoulder surgery may have derailed him last season, and who really knows whether the concussion he sustained in May has played a role in his respectable yet unspectacular 2019 season?

Grade: C+

Zack Wheeler

The right-hander is the Mets’ biggest trade chip heading to July 31, even with his first-half inconsistency. Wheeler can be ace-level for three or four straight starts, with dazzling stuff, but then has a tendency to slump for the next two or three, which explains his 4.69 ERA. Usually it’s one bad inning that derails him.

Grade: C+

Wilson Ramos

It’s not a good sign that deGrom and Noah Syndergaard would prefer Tomas Nido behind the plate. Ramos looks more and more like a DH. Ramos’ struggles blocking balls in the dirt and his pitch framing are the biggest issues. But at least the Mets got a decent bat for two years and $19 million, and Ramos’ .757 OPS is acceptable.

Grade: C+

Tomas Nido

A fourth option behind the plate as spring training began, the second-year catcher has emerged and earned praise for his handling of deGrom and Syndergaard, in particular. Nido doesn’t bring much pop to the lineup, but also isn’t the automatic out he was earlier in the season.

Grade: C+

Noah Syndergaard

The stuff remains electric, the results not so much so. Syndergaard had trouble gripping his slider early in the season and still hasn’t regained full confidence in that pitch. Syndergaard’s 4.68 ERA is alarming for a team that has needed him at deGrom level to help compensate for the bullpen’s woes.

Grade: C

Justin Wilson

The lefty reliever has barely pitched because of elbow issues. Few teams seem to have worse luck with free-agent relievers than the Mets.

Grade: C

Wilmer Font

The Mets were desperate when they acquired him from Tampa Bay in early May. The right-hander struggled as a fill-in starter, but has been acceptable from the bullpen, pitching to a 4.41 ERA in mostly low-leverage situations.

Grade: C

Adeiny Hechavarria

The veteran infielder arrived on a minor-league deal in spring training and has been a respectable backup at shortstop. For a stretch in late May when Robinson Cano was sidelined, he helped carry the Mets lineup.

Grade: C

Steven Matz

For the first two months of the season, the lefty was the Mets’ most consistent starting pitcher. It’s been a struggle since then for Matz, who arrived at the break with the highest ERA (4.89) among the team’s starters. Matz’s first-inning troubles are pronounced, and he’s been shellacked in his two starts in Philadelphia this season.

Grade: C–

Robert Gsellman

The right-hander was probably overused in May and June, especially during a stretch in which Lugo was sidelined. The Mets need better from Gsellman, who will begin the second half with a 5.09 ERA and 1.435 WHIP. He’s been a disaster at Citi Field, where opponents are batting .342 against him.

Grade: D

Brandon Nimmo

The outfielder slumped to begin his season and then started showing life before sustaining a neck injury and regressing at the plate. Nimmo has been on the injured list since late May with a bulging disk in his neck, and it’s unclear if he will play again this season. Nimmo’s absence has forced Conforto into almost full-time duty in center field.

Grade: D

Amed Rosario

It’s become evident that the third-year shortstop isn’t the All-Star material the Mets thought they had. Now the question has become: Is he an everyday major league shortstop? Rosario’s defense remains an issue — never mind his 12 errors, but getting to balls — and his offense has hardly compensated: a .260/.299/.414 slash line. Maybe the Mets will experiment with him in center field in the second half.

Grade: D

Robinson Cano

The Mets thought they were getting if not an All-Star, a dependable veteran who would serve as a focal point in the lineup. But the 36-year-old Cano has shown his age , both at the plate and in the field. The Mets would be a better team with McNeil at second base, but the team is also beholden to the four years Cano has remaining on his contract after this season.

Grade: F

Edwin Diaz

The worst part about the trade that sent Kelenic and Dunn to the Mariners hasn’t been Cano’s deterioration as much as Diaz’s maddening underperformance. The former All-Star closer arrived at the break with a 1-6 record, 5.50 ERA and four blown saves. The Mets were on the verge of climbing back to .500 when Diaz imploded in a loss at Dodger Stadium in late May, and it’s been a hellish ride for the team and player since.

Grade: F

Jeurys Familia

Diaz has pitched like Mariano Rivera compared to Familia, whose second stint with he Mets has been nothing short of disastrous. Familia owns a 7.50 ERA and 1.83 WHIP in the first season of a three-year contract worth $30 million.

Grade: F

Juan Lagares

He’s finally remained healthy, but Lagares is a shell of the player who won a Gold Glove award for the Mets in 2014 and he’s brought nothing to the equation offensively. Trading him will be difficult. He is owed $4 million over the remainder of the season.

Grade: F

Jed Lowrie

Who?

Grade: Incomplete

Mickey Callaway

He’s managed to avoid getting fired, but lost pitching coach Dave Eiland and bullpen coach Chuck Hernandez, who were axed last month. Callaway’s insistence — is it really his call? — on leaving Cano in the No. 3 hole hasn’t helped the lineup.

Grade: F

Brodie Van Wagenen

Come get us? The rest of the league came, saw and conquered. Among Van Wagenen’s failings was overestimating the amount of talent and depth in a bullpen that might be the worst in the major leagues. The Post also reported last month that the rookie GM was responsible for dictating at least one in-game decision to manager Mickey Callaway, with an order to remove Jacob deGrom from a start. And last weekend Van Wagenen melted down following a loss and ripped his coaching staff during a meeting punctuated by the GM throwing a chair.

Grade: F