The Mets are in trouble.

Not only did they put Johan Santana, their ace lefthander, on the 15-day disabled list with a sprained right ankle Saturday, but they also lost the seventh of their eight games since the All-Star break, falling 8-5 to the Dodgers at Citi Field

Santana (6-7) moves to the disabled list after Friday's third rocky start in a row. He allowed seven hits -- including home runs by Matt Kemp and Luis Cruz -- three walks and six earned runs in three innings. He joins starting pitchers Dillon Gee and Mike Pelfrey on the DL, along with reliever Frank Francisco and outfielder Mike Baxter.

Manager Terry Collins said Santana's ankle was worse than initially thought, and since suffering the injury two weeks ago, Santana's motion has been affected.

"Ever since he's had the ankle injury, basically his command has not been there due to the fact that he cannot land properly," Collins said. "He's using all arm to pitch with, causing some fatigue in his shoulder. No pain. There's just nothing there."

The loss of Santana could pave the way for the Mets to call up Matt Harvey from Triple-A Buffalo, but their immediate focus is getting their ace healthy. And Harvey was hit hard Saturday night, allowing six runs and seven hits in five innings in Buffalo's 11-0 loss to Charlotte.

Santana, who missed all of 2011 after shoulder surgery, injured his ankle against the Cubs on July 6 when Reed Johnson stepped on it as Santana tried to cover first base. Since his June 1 no-hitter, he has allowed 31 earned runs in 422/3 innings, and he has yielded 11 home runs.

"We think that the ankle injury may have led to some general fatigue, in the shoulder specifically," general manager Sandy Alderson said. "In light of the surgery and where he's been, and in light of what he's accomplished, we've gotten to the point where he probably needs to get that ankle right and get back to the point where he feels confident about pitching."

Santana admitted he felt some pain in his ankle a few times, then quickly added that he's so focused on the mound that he couldn't tell he was compensating his delivery because of it. However, after reviewing video footage of Santana's starts since he got banged up, the Mets pointed out the difference to him and decided it was best to give Santana time to get himself right.

"I'm OK," Santana said. "My ankle is still recovering from that injury, that day. But again, I don't think about it. My shoulder is fine, I don't have any problems with it. We'll see the next couple of days how it feels and see what the next step will be and what kind of plan we have.

"It's tough," he added. "I didn't want to go on the DL. I wanted to keep pitching and competing. But at the same time, they have a decision and we agreed to it."

The Mets' pitching plight was evident Saturday as the Dodgers knocked out Miguel Batista, who himself had been on the DL earlier in the season, in just three innings.

He used five pitchers and needed R.A. Dickey, who had started and pitched 71/3 innings Thursday, to finish the game. The knuckleballer, who is the only Met to win a game since Gee on July 7, faced five batters in the ninth inning and gave up a two-out, two-run homer to Juan Uribe.

"We've got to get ourselves in a situation where we get deeper in games," Collins said.

Is Harvey, the team's top pitching prospect, the answer? The 6-4 righthander is 7-5 with a 3.68 ERA at Buffalo? Or will the Mets try to call up a reliever or try to find help elsewhere?

"Yeah, we have take a look at where we are," Alderson said. "We are filling two spots and instead of one. So certainly he would be a possibility and we'll have to look at the other options and make a decision in the next couple of days."

Jonathon Niese (7-4, 3.58 ERA) pitches Sunday against the Dodgers.

"We've got our guy [Sunday, who] has been pitching great," Collins said. "I know he's going to get us deep in the game and we'll be able to settle our bullpen down a little bit."

With James Crepea