The Mets will likely be without Jose Reyes until Friday night — at least.

“We’re going to take it day by day and see what happens,” said Reyes, who has a strained left intercostal. “Today is going to be a treatment day, put some ice on it, and see how I feel tomorrow and try to go from there.”

But manager Terry Collins said that he intends to be conservative with the 33-year-old Reyes, who is hitting .239 in 16 games since reuniting with the Mets.

“Even though he still feels it today, my guess is . . . we would probably be very careful tomorrow if he’s OK,” Collins said.

Wilmer Flores will step in for Reyes at third base against both righties and lefties. But Collins also left open the possibility that Flores plays shortstop in case Asdrubal Cabrera needs a breather in the next few days.

Either way, Reyes’ injury opens the door for Flores, who has seen only limited action despite hitting .340 in July with seven homers, the third most of any player in baseball during that span.

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Collins has generally shielded Flores against righties, who have held him to a .666 OPS this season compared with a 1.068 against lefties.

Said Collins: “If he stays with that game plan, he’ll have a lot more success against righthanders.”

Reyes said he felt that something wasn’t quite right on his fourth at-bat of the Mets’ 3-2 loss to the Cardinals in the first game of Tuesday’s doubleheader. But Reyes ignored it only to feel the sensation again in his fifth and final at-bat.

For a moment, he though the injury could have been worse. Last April, he fractured a rib in his left side, an injury that cost him nearly a month. He has at least escaped that fate, though the Mets must once again play shorthanded until he returns.

“Thank God my rib’s fine,” Reyes said. “It’s just the muscle.”