PORT ST. LUCIE — Brandon Nimmo jumped into Grapefruit League action a bit earlier this year in part because this type of thing might happen.

Nimmo, who has been recovering from plantar fasciitis, began his exhibition season Friday — in late February, when early March had become his norm — so he could see how his foot would react and give him additional time if the process did not go smoothly.

As it turned out, his knee needed more time.

Nimmo felt some right knee soreness Saturday that pushed him out of Sunday’s lineup and has slowed his progression.

He is expecting to take it easy for a few days and reassess his knee Thursday, which is three weeks before the season opener.

There is time, and Nimmo is not worried.

“I’m not overly concerned,” Nimmo said after he hit, threw and ran Monday, the running at 70 percent. “In fact, today was really good, a really positive day. I’m really positive going forward with this, but I also know that it’s not 100 percent — I got to take it day by day.”

Spring soreness happens, but there is extra attention paid to Nimmo, whose plantar fasciitis carried over from last season and who has been slowly building up before running at 100 percent.

After playing a few innings Friday and getting two plate appearances, the progression has been slowed.

Nimmo still believes he will be ready for Opening Day.

“It just flared up a little bit on me,” Nimmo said. “Let’s nip this in the bud before we take the next step.”

Starling Marte is “feeling really good,” manager Carlos Mendoza said, after taking cuts in his first live batting practice Sunday.

The next step is “hopefully” playing in a game in the next few days.

It is unclear whether Marte, who has been dealing with knee soreness since last summer, will play in a minor league or major league game, and it is possible that he initially serves as DH, but the step would indicate progress.

The fourth outfielder/platoon DH participated in outfield drills Monday.

Mendoza is not sure whether top prospect Drew Gilbert, who is in major league camp, will get into Grapefruit League games.

The outfielder missed much of last season to a hamstring strain.

He recovered and played at the end of the year and in the Arizona Fall League, but the Mets are being careful in his progression.