Rotation or pen, Lugo a vital arm

Seth Lugo doesn’t know yet whether he will head back to the bullpen or stay in the Mets’ rotation, but his spot start Thursday night certainly left a good impression.

After spending the first two months of the season emerging as a valuable relief weapon, Lugo made his starting debut Thursday and tossed four scoreless innings before the Mets’ bullpen got tagged in a 5-1 loss to the Cubs at Citi Field.

“I think [Lugo] was really good,” manager Mickey Callaway said.

Filling in for Jason Vargas, who pitched on short rest Tuesday in place of the injured Noah Syndergaard, Lugo gave the Mets exactly what Callaway had hoped for: four innings and 60 pitches, allowing three hits and striking out three while pitching on two days’ rest.

Callaway declined to say if Lugo would remain in the rotation. That decision could come Friday after lefty Steven Matz, who has a strained middle finger on his pitching hand, throws a bullpen session to see if he can make his scheduled start Sunday.

“I think [Lugo] can definitely start,” Callaway said. “For us, in an ideal world, he’s still in the bullpen helping our bullpen and some of the other guys are in the rotation.”

With a pair of days off scheduled for next week, as long as Matz comes out of his bullpen session healthy the Mets wouldn’t need a fifth starter until June 16, at which time Syndergaard is expected to be off the disabled list. But the club also could decide to permanently move Lugo to the rotation and flip Vargas (8.53 ERA) to the bullpen.

Lugo said his preference is to remain a starter, but he did not view Thursday’s outing as an audition for the rotation.

“I’ve always been a starter,” he said. “[I’m] a lot more comfortable starting games, so it was nice out there tonight.”