MLB

Santana’s bullpen session irks Mets manager

PORT ST. LUCIE — Although Johan Santana came out of it in one piece, manager Terry Collins wasn’t thrilled with the impromptu bullpen session the lefty threw Sunday, and Collins let him know it yesterday.

“I asked him, ‘What did you get on the mound for?’ ” Collins said. “[Santana responded] ‘Because I felt good.’ It was unnecessary. In retrospect, he knows he could have handled it a little bit differently, but he’s fine and he wanted to show everybody he was fine.”

Santana threw a long-toss session again yesterday and pitching coach Dan Warthen expects Santana to throw another light bullpen session tomorrow — this time, with permission.

“He worked hard out there,” Warthen said. “He came out of it very well.”

PHOTOS: METS SPRING TRAINING

Collins was concerned Santana might have been inviting trouble — which is what the manager told him.

“The last thing I need is have you wake up tomorrow stiff,” Collins said of the conversation. “And take a huge step backwards just to prove to everybody you’re OK. I understand what you’re doing, but once in a while, let stuff slide.”

As for Santana, he said: “I’m good and that’s all I’ve got to say right now.”

Santana has been displeased that his offseason regimen has been questioned, since he hasn’t been able to make a start yet this spring.

Jeremy Hefner, who could slide into a starting spot if Santana begins the season on the disabled list, gave up a solo homer to Justin Upton, but was solid in a 4-2 loss to the Braves. He surrendered just one run in three innings.

* Kirk Nieuwenhuis might be back in less than a week after an MRI on his left knee revealed only a bone bruise. He injured it diving into second base in Jupiter on Sunday. There had been concern he had suffered ligament damage.

“I’ve got to wait and see how it responds [to anti-inflammatories],” said Nieuwenhuis, who is competing for a platoon spot in center. “I’ve missed a lot of time with other injuries, so it’s a relief this isn’t more serious.”

* Zack Wheeler, who was scratched from his last start because of a mild oblique strain, is expected to play catch the next two days and then throw a bullpen session either Thursday or Friday.

“We’re going to err on the side of caution with this guy,” Collins said. “He’s not going to make the club, anyway.”

dan.martin@nypost.com