JUPITER, Fla. — In what was expected to be a tuneup before he was set to leave the Mets for the World Baseball Classic, Jose Quintana sustained a poorly timed injury.

The Mets lefty reported left side tightness, general manager Billy Eppler said, after Quintana threw a scoreless inning in a 7-1 win over the Cardinals at Roger Dean Stadium on Sunday.

Quintana will undergo testing Monday, Eppler said.

Hours after the injury, the 34-year-old from Colombia announced he will not be able to represent his home country in the tournament.

“Now all I need is to get completely recovered and try to be ready for the beginning of the 2023 MLB season,” Quintana wrote in Spanish on Instagram.

Buck Showalter said Quintana had not complained about his side previously.

“Really too early to know the severity of it. We’ll see,” the Mets manager said. “I’m glad he told us.”

Quintana, signed to a two-year, $26 million pact this offseason, is a middle-of-the-rotation starter who has been dependable through an 11-year career and finished last season at his best, posting a 2.01 ERA in 12 second-half starts with the Cardinals.

This spring, though, has not started smoothly.

In his Grapefruit League debut Tuesday, Quintana allowed five earned runs on four hits and a walk while recording just two outs against the Astros.

After the outing, Quintana cited the pitch clock as an adjustment but also said his location was poor.

Sunday, working in relief of Kodai Senga, Quintana appeared more comfortable while completing a 13-pitch perfect frame punctuated by a strikeout of Paul Goldschmidt.

Quintana’s velocity appeared on track, averaging 91 mph with his fastball.

If the injury affects Quintana’s regular-season status, the Mets would have to test their rotation depth right away. Behind Max Scherzer, Justin Verlander, Senga, Quintana and Carlos Carrasco are swingmen David Peterson and Tylor Megill.

Peterson hurt his left foot Saturday, when he was hit by a comebacker, but the lefty is day-to-day after tests confirmed it was a contusion.

Beyond Peterson and Megill are Elieser Hernandez and Joey Lucchesi, both of whom have options and thus are expected to begin the season at Triple-A Syracuse to stretch out as potential rotation help.