MIAMI — The Mets’ youth movement, in full swing, included the promotion Friday of a second pitching prospect to the major league roster in the last week.

Jonah Tong, familiar to the club following his major league stint late last season, was recalled from Triple-A Syracuse and pitched three hitless innings in relief, with one walk, without allowing a run in the Mets’ 2-1 loss to the Marlins.

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“Very encouraging,” manager Carlos Mendoza said of Tong’s performance. “The velo, the fastball, the way it was playing, the changeup was good. He attacked. He gave us a chance.”

The right-hander pitched behind opener Tobias Myers and bulk reliever Sean Manaea, as team brass decided on lengthening the rotation to give the starters an extra day of rest. Freddy Peralta will start Saturday before Christian Scott gets the ball a day later.

Tong pitched to a 7.71 ERA in five starts for the club last season, when he was part of a rookie infusion that also included Nolan McLean and Brandon Sproat (who was traded to Milwaukee in the offseason).

On Wednesday, the Mets utilized another rookie, Zach Thornton, who allowed four earned runs over 4 ¹/₃ innings in a loss to the Nationals in his major league debut.

Tong had a 5.68 ERA in nine starts for Syracuse this season, striking out 55 batters in 38 innings.

Craig Kimbrel was designated for assignment to create roster space for Tong.

Juan Soto had a memento in his spare locker in the visitor’s clubhouse: second base from a day earlier at Nationals Park. On Thursday, Soto stole his 100th career base.

Soto began the night with five stolen bases this season.

Last season he stole a career-high 38 bases.

He missed nearly three weeks in April with a left calf strain, but manager Carlos Mendoza said Soto is clear to steal bases as he chooses.

“He’s playing the game, and if we get opportunities we’re going to take advantage,” Mendoza said. “It’s got nothing to do with the calf; he’s in a pretty good place.”

On the milestone, Mendoza added: “It’s a special number. When you look back, that is not easy; a great player that we’re watching here in front of our eyes.”

Kodai Senga threw 63 pitches over 3 ¹/₃ innings and allowed two earned runs on four hits and one walk with two strikeouts for Single-A St. Lucie in his first rehab start since he was placed on the injured list last month with spinal lumbar inflammation.