MLB

Pelfrey’s decision to pitch to righty backfires

MIAMI — Mike Pelfrey had Logan Morrison coming up to the plate with men on second and third in the fourth inning last night and decided to pitch around him.

Pelfrey preferred to face John Buck instead.

“I thought it was a better matchup,” Pelfrey said.

The Met righty’s strategy involved three factors:

* Buck bats righty, while Morrison hits lefty.

* Pelfrey believes his sinkerball is more effective against right-handed batters than it is against lefty-swinging ones.

* The Marlins had men on second and third. The double play wasn’t a possibility at that point. But, if Pelfrey walked Morrison and faced Buck, it put the double play in play.

So Pelfrey issued what he called an “unintentional intentional walk” to Morrison, handing him first base on five pitches and loading the bases for Buck. And on the eighth pitch of that at-bat, the Marlins catcher drilled a fastball for a grand slam over the right field wall — helping, along with Josh Johnson’s pitching, to deliver the Mets an Opening Night 6-2 loss at Sun Life Stadium.

Pelfrey suffered the defeat, and he hardly had what one could consider a strong night on the mound.

The 27-year-old — the team’s default ace with Johan Santana on the disabled list — had a mediocre outing in his first career opener. Pelfrey lasted just 4 1/3 innings, surrendering five runs on four hits and four walks. He threw 97 pitches in less than five innings of work.

“I just made some bad pitches,” Pelfrey said.

It’s a far different beginning for Pelfrey than last season. In his first five outings last year, Pelfrey went 4-0 — and picked up a save in the Mets’ 20-inning win over the Cardinals. Surprisingly, pitching coach Dan Warthen said Pelfrey’s spring training was better this season than last season.

“Obviously he didn’t have his good sinker going tonight,” manager Terry Collins said. “When they’re fouling balls straight back, it means he didn’t have the end of his sink. But I thought he battled very, very hard. Outside of one swing of the bat, he kept us in the game.”

He also keeps falling short against the Marlins.

At this point, Pelfrey’s futility against Florida is remarkable — there have been 74 pitchers ever to have made 10 or more starts against the Marlins in their careers. Pelfrey is now 1-7 with a 5.63 ERA in 13 games against the Marlins, owning the fewest wins. That lone victory came in his major league debut back in 2006.

Pelfrey was amped up for last night’s start and admitted to having some adrenaline. Warthen believed he had a lot of it.

“I think he was overthrowing,” Warthen said.

After the game, Collins told Pelfrey: “Hey Mike, we’ll get you some runs next time.”

Pelfrey didn’t get that, or the double play he needed.

mark.hale@nypost.com