If the Mets aren’t going to get to the playoffs, they can at least make it more difficult for teams still in the race.

That’s what they did against the Cubs, who had won five of six after the trade deadline before they arrived Monday at Citi Field. The Mets beat them Wednesday night, 4-3, to win the series after they came in having lost six straight games.

And as long as the Mets have Pete Alonso in the lineup, they have a chance to make waves. Alonso homered for the fourth time in three games against the Cubs with a fourth-inning, two-run blast that tied the score at 2-2.

Jeff McNeil then hit a go-ahead homer to lead off the sixth after Alonso’s 35th blast of the season put some life into what had been another quiet night at Citi Field.

The Mets held on even after Adam Ottavino allowed a homer and left with two on and no out in the ninth. Phil Bickford retired three of the four batters he faced to pick his first save with the Mets.

After a sacrifice bunt by Nick Madrigal moved both runners up, Bickford struck out Christopher Morel. He then walked Nico Hoerner, but fanned Ian Happ to end it.

Alonso, meanwhile, could make a run at 50 homers for the second time in his career, despite what has been an inconsistent season.

“You look at numbers and they don’t necessarily tell the whole journey of a season,” Alonso said. “That’s how people look to define a season, but the process of how I found success this year is definitely different than in years past.”

He continued his belated resurgence after he had gone through a lengthy dry spell from the end of May until mid-July, with a .554 OPS over a 34-game span, a stretch he called “definitely the worst of my big league career.” He snapped out of it with a pair of five-RBI games in late July and his power surge has continued.

“I don’t think people realize how much him struggling when the team struggled hurt him,’’ manager Buck Showalter said before the game.

Lately, Alonso has been back to his usual form and said again his sprained wrist hasn’t been an issue.

“I’ve been healthy the whole time,” Alonso said, adding that a “simplified” approach at the plate has helped him turn his season around.

His recent spurt also gave Alonso 181 homers for his career, good for fifth on the all-time franchise list and seven behind Howard Johnson, who’s in fourth.

“It gets your attention,” Showalter said of Alonso’s march up the list. “There have been some great hitters here with power. Pete’s doing it in a ballpark where you have to earn every one of them.”

Darryl Strawberry’s franchise record of 252 homers is well within reach for the first baseman — if he sticks around in Queens. Alonso can be a free agent for the first time after next season.

“He’s gonna have quite a legacy when all is said and done,” Showalter said. “He already does.”

But this season won’t help Alonso’s postseason numbers, since the Mets will be playing out the string for the next seven-plus weeks.

Aside from seeing if Alonso can stay hot, the Mets also will be looking at David Peterson, who is back in the rotation after the trades of Max Scherzer and Justin Verlander.

The lefty made his second start since his brief stint in the bullpen and wasn’t especially effective. Peterson gave up a homer to Morel with his first pitch of the game, but then struck out the next three hitters and left after giving up two runs in 3 ²/₃ innings.

The Mets took the lead in the sixth inning against former Yankee prospect Hayden Wesneski, who allowed all four batters he faced to reach base. McNeil put the Mets up with a home run to start the inning and they added a run on a single by Jonathan Arauz to make it 4-2.