PHILADELPHIA - Johan Santana had plenty of regrettable moments during last night's game at Citizens Bank Park, where the Phillies delivered one of the most brutal beatings in his 11-year career.

Santana allowed a career-high 10 runs, including nine in the fourth inning. He served up a career-worst four homers, the lowlight being a grand slam to Shane Victorino.

But rock bottom for Santana had to be his staredown with 47-year-old Jamie Moyer, whose bases-loaded walk with two outs triggered the entire fourth-inning catastrophe that was responsible for the Mets' 11-5 loss to the Phillies.

"It was just a rough night," Santana said. "My fastball was moving all over the place. It was one of those days that things didn't work out the way I wanted them to."

Neither did the weekend for the Mets, who took Friday's opener to extend an eight-game winning streak only to get outscored 21-5 over the next two humbling defeats in handing the NL East lead back to the Phillies. The Mets also had their first losing streak since they dropped two in a row April 13-14 in Colorado.

"We know we can play with them," Jeff Francoeur said. "We still feel pretty good with what we have as a team."

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Seeing their ace pounded, however, had to be unsettling and the way Santana unraveled in the fourth inning - even before Moyer - was shocking. Santana had two outs and a 1-and-2 count to Raul Ibañez, but left a fastball down-and-in, right where Ibañez could pull it to rightfield for an RBI single.

That was the first sign to Santana that he was losing command of his fastball. After a single by Juan Castro, Santana didn't mind pitching around Carlos Ruiz to load the bases with Moyer up next. But Santana immediately fell behind 2-and-0 to Moyer, then 3-and-1 before a foul ball pushed the count full. Moyer then took an inside fastball and the seven-pitch walk - all fastballs - forced in a run that trimmed the Mets' lead to 5-4. "When he wanted to throw the ball down the middle, he couldn't," catcher Rod Barajas said. "For some reason, he lost control and we weren't able to make an adjustment to get it back."

Santana insists he is perfectly healthy, but it was strange for a two-time Cy Young winner to look as helpless as he did.

"It happened so quick," Francoeur said. "But I'll still take Santana on the mound any day of the week. How many times is that going to happen?"

After the walk to Moyer, Santana allowed Victorino's slam and a single to Placido Polanco before Chase Utley's two-run homer made it 10-5. The 10 runs were the most given up by Santana since the Yankees ripped him for nine last June 14 and the most by a Mets pitcher since Orlando Hernandez allowed 11 against the Phillies in 2006.

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"It happens," David Wright said. "It just goes to show that he's human just like the rest of us. He's going to have bad days. You'd like to think that he's a machine and that he never makes a mistake. But he's human."

It took two days to rob the Mets of their April momentum and to some extent, rattle their faith in the top two starters. On Saturday, Mike Pelfrey allowed six runs in four innings in a 10-0 loss that pushed his ERA from 0.69 to 2.40. The Phillies provided a similar slap in the face to Santana, whose 2.08 ERA jumped to 4.50.

Santana's fourth-inning meltdown was a stunning turnaround for the Mets, who wasted leads of 3-0 and 5-2. David Wright, who entered the game batting .426 (20-for-47) with three homers against Moyer, took him deep for a three-run shot in the first inning.

But the Phillies answered with home runs from Polanco and Ryan Howard in the bottom of the first. Santana shook it off by retiring the next seven batters and Barajas provided what the Mets thought was breathing room with a two-run homer in the fourth. That was before Santana completely collapsed in the bottom half.

"That's uncharacteristic of Johan," Jerry Manuel said. "But he's a fighter, and a competitor, and I know he'll bounce back."