Starting pitcher Mike Pelfrey reacts in the dugout after being...

Starting pitcher Mike Pelfrey reacts in the dugout after being removed from the game against the Arizona Diamondbacks. (July 19, 2010) Credit: Getty Images

PHOENIX — Mike Pelfrey was bumped from his scheduled start Saturday after complaining of a stiff neck, so it didn’t help Monday night that he probably developed whiplash from watching the Diamondbacks spray his pitches to every corner of Chase Field.

As bad as Pelfrey was, it was made worse by the fact that he had to be pulled after only four outs, and the 11/3-inning stint was the shortest of his career. Pelfrey’s stay was brief, but Arizona smacked him around for six runs, and the revamped Mets lineup failed to come up with a counterpunch in the 13-2 loss.

“Physically I feel good,” Pelfrey said. “I’m just going through one of the worst stretches in my life. It’s frustrating. I think I’ve gotten away from establishing my fastball; it seems like I’m trying to establish three or four pitches at once. That’s not who I am.”

But just who is Pelfrey (10-5) at this point? The confident pitcher who flirted with an All-Star bid after surging to 10-2 in the first half? Or is he the Pelfrey of the last four starts, during which he is 0-3 with a 12.89 ERA, and has failed to finish the fifth inning each time. Over that stretch, Pelfrey has allowed 40 hits and 10 walks in 142/3 innings.

“No doubt about it, it’s concerning,” said manager Jerry Manuel, who spoke with Pelfrey about the need to focus back on his fastball. “We’re talking about a young man that we felt was an All-Star pitcher, and to have those outings, those outings that he’d had here lately, that’s very discouraging because he’s a guy we’re counting on very heavily down the stretch to do what we need to do.”

With Pelfrey’s collapse, the Mets slipped to 1-4 on this 11-game road trip and if not for Sunday’s gift from plate umpire Phil Cuzzi, they’d be winless to this point. They also dropped to 4-10 in their last 14 road games and 8-14 overall. Since the All-Star break, they’ve also lost 1½ games in the standings and sit 5½ behind the Braves, who did not play Monday night.

The Mets were supposed to be energized Monday night by the addition of Jose Reyes and Luis Castillo, who joined Carlos Beltran and David Wright for a lineup that had not played together since May 20 of last season in Los Angeles.

That was the idea, anyway. Instead, the focus soon shifted to Pelfrey, who needed 51 pitches to barely survive the first inning as the D-backs pummeled him for four runs. Pelfrey’s shortest outing before Monday night was three innings, which he had done twice, and most recently July 7 of last season against the Dodgers.

Pelfrey’s implosion was unsettling enough if it had been one isolated incident. But this has become a startling trend for the Mets’ No. 2 starter.

“Fifty-one pitches in an inning is ridiculous,” Pelfrey said. “The biggest thing is stay positive. I know sometimes that’s harder to do when things are going the way they’re going, but I’ve got to take the positive and try to move on.

“I definitely know this isn’t acceptable. I made it extremely tough on the team. I’m sure everyone felt like they got kicked in the stomach. I definitely need to turn it around and need to do it very quickly.”

Monday night, he was fortunate — or perhaps not so much — to survive the first inning. Immediately after a visit by pitching coach Dan Warthen, Mark Reynolds drilled an RBI triple. Manuel got Raul Valdes up in the bullpen right before Gerardo Parra smacked a run-scoring single to make it 4-0.

Manuel let Pelfrey hang on to retire the pitcher, Ian Kennedy, on a bouncer back to the mound. In retrospect, the manager never should have let him come out for the second inning. Arizona’s barrage continued with three more hits, including Justin Upton’s RBI double.

As for the Mets’ reinforcements, they had a mixed night, as well. Reyes, who missed the previous five games to let his oblique strain heal, committed a pair of errors in the first two innings. But he also had two hits, including an RBI double in the ninth inning.

The first came when Reyes failed to finish a double play, throwing wild to first base, and the D-backs scored on the first-inning miscue. In the second, Reyes inexplicably let Rod Barajas’ throw down to second shoot right past him on a steal attempt and that sparked Arizona’s two-run rally.

Castillo and Beltran were more encouraging. Castillo fielded his position well, singled in his first at-bat and appeared to be running OK. Beltran also had a hit, but came up short when the Mets really needed one. In the fifth inning, with the Mets trailing 6-1, they had runners at second and third with two outs, but Beltran popped up to leftfield.