MILWAUKEE -- The Mets were more than glad to leave Wisconsin.

When Garrett Mitchell hit a walk-off homer against Adam Ottavino on Wednesday to send the Mets to a 7-6 loss and a three-game series sweep in Milwaukee, they fell to 3-18 in their last 21 games at American Family Field.

“There’s a lot of things we could do better,” first baseman Pete Alonso said.

Which of those is most concerning at the moment? The Mets may have issues up and down the roster, but they’re not all equal.

Offense
Key stat: 3.3 runs/game, down from 4.8 last season
Concern level: Low

The most encouraging aspect of Wednesday’s finale was the emergence of both Alonso (two home runs) and Francisco Lindor (three hits, two doubles). That duo drove home all six of the Mets’ runs and scored four of them, laying to rest some early narratives about the impotence of New York’s offense.

Some lineup concerns do linger, particularly at third base, where manager Buck Showalter has given Eduardo Escobar two consecutive off-days against right-handers due to a 1-for-16 start with seven strikeouts. But even if Escobar continues to struggle, prospect Brett Baty will be an option now that his thumb scare at Triple-A Syracuse turned out to be minor.

This offense does have limits, particularly in the power department. But it’s still one of the better units in the league, with Alonso, Lindor, Jeff McNeil and Brandon Nimmo all in their primes. Keep in mind that the Mets spent the first week of the season facing some of the game’s best pitchers, including Sandy Alcantara, Jesús Luzardo and Corbin Burnes.

“I believe in every single guy that we have,” Lindor said. “I think we have what it takes. We have the ‘it’ factor.”

Bullpen
Key stat: 4.44 ERA, up from 3.50 last season
Concern level: Medium

The easy narrative revolves around the fact that Edwin Díaz is missing, isn’t likely to return this season and isn’t replaceable. All that is true. But the walk-off Ottavino’s allowed on Wednesday was less the result of his being thrust into an unfamiliar role -- the veteran right-hander has seen myriad high-leverage spots throughout his career -- and more because of some early usage hiccups.

Earlier this week, Ottavino warmed multiple times without getting in a game. On Wednesday, Showalter used David Robertson -- more of a crossover weapon than Ottavino -- in the eighth inning to face lefties Jesse Winker and Brice Turang. That left Ottavino a bit exposed with two other lefties waiting in the ninth.

“The location, it could have been a little more up or a little more in,” Ottavino said of his cutter to Mitchell.

Bigger picture, the Mets seem to have found a genuine weapon in John Curtiss, who pitched two scoreless innings earlier in the game. Ottavino and Robertson both have strong track records of success. And if the Mets wind up needing help midseason, relief pitching is always the easiest thing to find on the trade market. The situation here isn’t perfect, and reasons for concern do exist, but Wednesday’s loss doesn’t seem like something that should develop into a trend.

Starting pitching
Key stat: Two players on the injured list
Concern level: High

There remains no timeline for Justin Verlander's return from a teres major strain. José Quintana won’t debut until at least July. Max Scherzer has a 6.35 ERA, Kodai Senga still has plenty to prove and Carlos Carrasco experienced a notable velocity drop in his first start.

The rotation, in other words, has issues, and there is no obvious path for the Mets to correct them. Their most urgent hopes are for Scherzer to revert to prime form while Verlander progresses back from injury quickly. That would allow the Mets to ease pressure off David Peterson -- who walked five batters and allowed five runs on Wednesday -- and Tylor Megill.

“I’ve got to pound the zone more,” Peterson said. “And then the ones they hit were missed spots. I’ve got to clean those up to give the team a chance to win next time.”

Unlike on the offensive side of things, where prospects Baty, Mark Vientos and Francisco Álvarez could all step in if needed, the Mets don’t have any blue-chip pitchers in the upper Minors.

That’s just the way things are going right now for the Mets, who sent Megill back to New York City early in preparation for his home opener start on Thursday, which was later postponed to Friday because of weather. The only problem? Megill’s flight was delayed multiple times, forcing him back onto the team charter instead.

“It’s such a routine season, and we haven’t really been able to get into it yet,” Showalter said. “But nobody wants to hear it. Guys will sleep on the plane and a little bit at home, and look forward to a nice day.”