ST. LOUIS — Pete Alonso is off to a nice start in defending his NL Player of the Month title. 

After being recognized for his outstanding performance in March and April, the powerful first baseman quickly got back to work in helping the Mets break a two-game losing streak.

While the Mets displayed good hitting throughout the game, Alonso’s home run in the fifth inning boosted the team to a 9-3 win against the Cardinals at Busch Stadium.

Alonso launched a two-run, go-ahead blast in helping the Mets win their ninth straight game against the Cardinals dating to last season.

It’s the Mets’ longest winning streak against their former division foe. 

“The season is long, but having a strong month feels great. I aim to maintain this momentum and contribute towards winning more games,” Alonso mentioned before the game.

Alonso posted a 1.131 OPS in March/April and carried the lineup during a stretch in which Juan Soto, Brandon Nimmo and Mark Vientos, in particular, were slow in getting started offensively. 

On this night, all were contributors: The Mets totaled 17 hits. 

Clay Holmes received the win after allowing three earned runs on eight hits with three strikeouts over six innings.

The Cardinals jumped on Holmes early before he completed his outing by retiring 10 of 11 batters. 

Masyn Winn delivered an RBI single in the first that put Holmes in a 1-0 hole.

Lars Nootbar doubled leading off for the Cardinals and stole third to start the rally. 

Nimmo walked leading off the second against Sonny Gray and scored the Mets’ first run on Jeff McNeil’s ground out with the bases loaded.

Francisco Alvarez’s ensuing RBI fielder’s choice gave the Mets a 2-1 lead.

Jesse Winker and Vientos each singled in the inning behind Nimmo’s walk to load the bases. 

Alec Burleson hit a shot off Holmes’ ankle to reach on a single in the second inning.

Holmes, following a visit from manager Carlos Mendoza and the trainer, kept going and got the final two outs in the inning. 

But the Cardinals tagged Holmes for four singles in the third inning to put the Mets in a 3-2 hole.

Victor Scott II singled leading off and, after reaching second on a ground out, stole third and scored on Alvarez’s errant throw.

After Winn and Brendan Donovan singled in the inning, Willson Contreras delivered a two-out RBI single. 

Alonso jumped on an 0-2 changeup from Gray in the fifth inning and smashed a two-run homer, clearing the center field fence.

The blast was Alonso’s eighth this season.

Soto doubled before Alonso’s homer, which gave the first baseman 30 RBIs in 33 games. 

The Cardinals provided a gift to the Mets later in the inning.

Vientos hit what should have been an inning-ending double-play grounder, but Contreras dropped Winn’s throw, allowing Nimmo to score.

Alvarez’s RBI single widened the lead to 6-3.

Nimmo and Jesse Winker had singled in succession to extend the rally following Alonso’s homer.

McNeil singled ahead of Alvarez’s RBI single. 

Gray was removed after 4 ¹/₃ innings in which he allowed nine hits and three walks.

He surrendered six runs, one of which was unearned. 

Nimmo padded the Mets’ lead with a homer leading off the seventh against John King.

It was Nimmo’s third homer of the week — he hit two Monday, including a grand slam, as part of his franchise record-tying nine-RBI performance against the Nationals. 

Alvarez stroked an RBI single in the inning that buried the Cardinals in an 8-3 hole. 

Alvarez’s third hit of the game helped the Mets score their final run, on Luisangel Acuña’s sacrifice fly in the ninth.