ST. PETERSBURG, Fla. — Robert Stock hasn’t found much middle ground in his starts, so his early success Monday night was a good sign for the Mets.

By the time the 36-year-old journeyman’s outing concluded, he had pitched the best game of his major league career, helping the Mets win their latest matchup against a first-place team.

Behind the right-hander’s 5 ¹/₃ scoreless innings, the Mets beat the Rays 3-2 at Tropicana Field.

The series is the Mets’ fourth straight against a division leader (White Sox, Brewers and Astros previously). The Rays began the night with the American League’s best record at 82-54.

Stock was torched for seven runs in his start against the Brewers last week but hardly resembled that pitcher on this night. Stock also had an outing in Pittsburgh last month in which he allowed eight earned runs.

Those two duds explain his 5.88 ERA even though he hasn’t allowed more than one earned run in any of his other four appearances since returning from surgery for thoracic outlet syndrome.

Stock is fighting to remain in the rotation as other options become available. Most notably, Justin Hagenman will be added to start Wednesday, giving Christian Scott extra rest, and Jonah Tong has shown big improvement at Triple-A Syracuse.

The Rays managed only five hits against Stock, who struck out five without walking a batter. The win was his third in a career that has spanned 63 appearances (nine as a starter).

Mark Vientos, fresh off a three-homer game on a minor league rehab assignment, gave the lineup a jolt with a seventh-inning blast in his return from the injured list. Vientos rejoined the roster on the day Luis Robert Jr. was claimed off waivers by the Orioles.

The Mets defense put Stock in peril in the fifth before saving him with the bases loaded: Christopher Morel’s leaping catch on Jonathan Arnada’s shot to left, which ended the inning, kept the shutout intact.

Jonny DeLuca and Richie Palacios each reached on an infield single in the inning. DeLuca’s grounder deflected off Bo Bichette’s glove, and Palacios hit a chopper that Francisco Lindor mishandled. But with the bases loaded, Stock got Taylor Walls to pop out and struck out Yandy Díaz before Morel’s leaping catch allowed him to escape unscathed.

Morel had a big play to conclude the following inning, throwing out Chandler Simpson attempting to stretch a single into a double.

Vientos’ double-play grounder in the fourth gave the Mets a 1-0 lead after Bo Bichette doubled and Carson Benge singled in succession.

In the seventh, Vientos delivered his 12th homer this season before Francisco Alvarez’s RBI single extended the Mets lead to 3-0. Morel and Marcus Semien each singled in the inning.

Liam Hicks and Simpson each stroked an RBI single in the eighth against Daniel Duarte that narrowed the Mets lead to 3-2. Chris Devenski retired Cedric Mullins for the inning’s final out with the tying run at third base. Kodai Senga earned the save with a scoreless ninth.