Jed Lowrie of the Mets works out on the field during summer...

Jed Lowrie of the Mets works out on the field during summer camp at Citi Field on July 15. Credit: Jim McIsaac

Jed Lowrie still isn’t ready.

The Mets put Lowrie on the injured list Monday with what they called “left knee discomfort,” the same mysterious problem that kept him out nearly all of last season. This will be the second time in as many years with the Mets that Lowrie, 36, won’t be healthy enough to play on Opening Day.

Manager Luis Rojas didn’t seem confident about anything after Opening Day, either.

“He’s worked really hard to get to where he is,” Rojas said. “After getting seen by our doctor, we expect to find out more. We’ll definitely reassess his position, as far as [being available at all in] 2020, after that.”

Regarding that trip to the doctor: 17 months after the Mets first mentioned Lowrie’s knee issue, the plan now is for him to visit Dr. David Altchek, the team’s medical director, “in the next few days or so,” Rojas said.

The goal of the appointment is to “establish a plan to progress him back,” Rojas added.

Lowrie had been working out with the Mets — while wearing a large brace on his left leg — but didn’t play in exhibitions against the Yankees over the weekend. Rojas said Lowrie, who was playing third base and second base, was having trouble with baserunning and playing defense.

“From a competition standpoint, it’s just not where we want it,” Rojas said. “After getting seen by our doctor, we expect to find out more.

“We saw his bat, we saw his ability. His hands, his arm, they’re all in shape. It’s just the running part, some also parts of his defense, moving around and the range to make some plays. That was the part that we just couldn’t translate in our vision into playing games.”

The Mets did not make Lowrie available for an interview. On July 5, when he most recently spoke to reporters, he declined to be specific about his injury diagnosis, saying he did not want to create a distraction.

It is not clear why Lowrie felt identifying the injury would create a distraction.

“Left knee discomfort is his diagnosis right now,” Rojas said Monday.

Is surgery an option?

“That I can’t say,” Rojas said. “That’ll be something that we’ll definitely reassess when we get something from our doctor.

“Our approach has been rehab [as opposed to a surgical solution]. He’s worked really hard. I can’t say that enough. He’s really worked hard to get here, to be in camp and to be able to play in games with guys.”

If Lowrie’s absence creates a hole in the Mets’ playing-time plans, it won’t be hard to fill. Luis Guillorme might make the roster as a utility infielder. Any of Eduardo Nunez, Gordon Beckham and Max Moroff — all in camp on minor-league deals — could fill a similar role. And if the Mets want or need to, they could use top shortstop prospect Andres Gimenez, who has dabbled at second and third, similarly.

However it plays out, Lowrie is proving not to be a good investment. During his first offseason as general manager, Brodie Van Wagenen signed Lowrie — his former longtime client — to a two-year, $20 million contract in January 2019. He went 0-for-7 last season.

Now Lowrie might not play at all in this 60-game season that begins Friday.

“It can definitely be tough, especially from a gamer like he’s been,” Rojas said of Lowrie, who has averaged 93 games per season in his 12 major-league seasons. “He’s known in history to be a gamer, a guy who plays the game really hard. Guys like that are going to go sometimes through some injuries like this. Unfortunate. But he’s worked really hard to get to where he is.”