PORT ST. LUCIE — Bobby Parnell is nowhere close to settling the debate over whether he can be a successful closer, but at least has avoided scaring the Mets about the situation this spring.

The fireballing righty, who was named the closer last month when it became evident Frank Francisco might not be ready for the season, has been among the best performers in camp.

“Just short of excellent,” pitching coach Dan Warthen said yesterday, when asked about Parnell’s spring. “I think he’s thrown the baseball as well as he wants to, his breaking ball has gotten better, he’s starting to use his changeup a little bit now — which most people don’t recognize — and also he’s locating.”

Parnell, who struck out the side in the ninth inning of the Mets’ 6-2 exhibition victory over the Astros last night, has a 2.31 ERA in 12 appearances this spring, with two saves in three chances. He will begin the season as the closer — Francisco hasn’t pitched in a game all spring because of a sore elbow — and be in position to keep the job if he succeeds.

Brandon Lyon also has closing experience, and the Mets could eventually groom Jeurys Familia if needed for the role, but are in no hurry to see anyone other than the 28-year-old Parnell receiving the vast majority of save opportunities.

Parnell said the fact the Mets told him early in camp he was the closer, instead of waiting to gauge Francisco’s progress, allowed him to develop the right mindset for the job.

“I feel like they have confidence in me, and to have that named right away was a big weight off the shoulder,” Parnell said. “I felt like I could focus on pitching instead of having to work to earn a spot. To have their confidence and be able to relax during spring training is big.”

Parnell was dominant in the final month of last season filling in for Francisco after having mixed results in the closer’s role for a six-week stretch beginning in late June. Overall, Parnell had seven saves in 12 chances last year.

“I felt pretty strongly about him last year, going into the season, but still worried about him being the guy we wanted late in the game,” Warthen said. “But I think that maturity showed up toward the end of last year and hopefully it will carry on for the rest of his career.”

Parnell began throwing a curveball last season, and said the pitch has further evolved this spring. He is now unafraid to throw the curve in a big situation instead of relying exclusively on his 97-100 mph heat.

Does Parnell agree with Warthen’s assessment of his “just short of excellent” spring?

“I feel like it’s been a decent spring,” Parnell said. “I feel like I picked up where I left off and I’m comfortable where I’m at. I don’t know about ‘excellent,’ but I feel like it’s good.”

Warthen said there have been numerous conversations with Parnell about not trying too hard in the closer’s role.

“Too many people try to do too much,” Warthen said. “They say, ‘Oh my God, I’ve got to close the baseball game,’ and they put an insurmountable amount of pressure upon themselves as opposed to saying, ‘I’ve got to do what I do. I’ve got to throw the baseball across the plate and I’ve got to execute pitches.’ ”