MLB

Joba delivers dud

SEATTLE — To most of the baseball galaxy, Joba Chamberlain’s outing yesterday was hard to look at.

Asked to prove he belongs in an important October role, and to help keep the Red Sox from advancing on the Yankees, Chamberlain was spanked in a 7-1 loss to the Mariners in front of 35,885 at Safeco Field.

In three innings, Chamberlain gave up seven runs, six hits and walked three (one intentionally).

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Yet while Chamberlain termed the outing “embarrassing,” he refused to believe he was anywhere as bad as the math indicated.

“I take a positive out of everything,” said Chamberlain, who is 0-2 with a hefty 7.88 ERA in five starts since the Yankees cut back his innings in order to keep him around 160 for the regular season.

He has logged 146 2/3 innings and has two more starts. He has given up 23 hits and seven walks (one intentional) in 16 innings.

“It’s going to take a lot more than this to get me down and to beat myself up,” he said. “My delivery was great, slider was great and fastball velocity great.”

Coupled with the Red Sox winning, the loss sliced the Yankees’ AL East lead to five games over their blood rivals, who are in The Bronx for three this weekend. That’s the smallest Yankees lead since they were up 4½ games on Aug. 7.

Their magic number over the Red Sox remained at nine. The magic number to clinch a playoff spot is one thanks to the Rangers losing.

“We have not played very well for nine [4-5] games,” said manager Joe Girardi, whose lineup could only score a run and collect four hits off Ian Snell (5-2) in 5 1/3 innings.

“We know that it is going to go down to the end. No one is going to hand you anything. I think our guys are frustrated that they are not winning many games.”

And it’s not getting easier. The Yankees open a three-game series against the AL West-leading Angels tonight in Anaheim. Then it’s the Red Sox in The Bronx.

With the Yankees likely to pick the “A” ALDS, they will require three starters in the first round. Should they advance, they could stick with three if they are willing to work pitchers on short rest.

If they need three, Chamberlain is going to land in the bullpen, where Phil Hughes has taken over and thrived in Chamberlain’s former role as Mariano Rivera’s set-up man.

“We expect him to be our fourth starter,” Girardi said of Chamberlain, who is 8-6 and hasn’t won since Aug. 6, when he beat the Red Sox, 13-6, despite giving up four runs and six hits in five innings.

Since Sergio Mitre, who provided five shutout innings yesterday, and Chad Gaudin, who is more suited for relief, are the only other options if Girardi goes with four starters in the playoffs, Chamberlain’s spot is secure if he is healthy. And he insists that’s the case.

“The slider velocity is up, the fastball velocity is more consistent and the change-up and curveball are great,” Chamberlain said. “It’s frustrating, but I feel great.”

With two starts remaining, Chamberlain needs to start showing that feeling great translates into pitching better.

He says having his innings cut back and pitching with extended rest at the beginning of the latest Joba Rules haven’t bothered him. However, catcher Jorge Posada acknowledged it’s hard to pull off.

“You don’t know how long you are going to pitch — it’s tough to pitch when you don’t know what’s going on,” Posada said. “It’s hard — three innings, 10 days — it’s hard to pitch like that.”

And hard to look at.

george.king@nypost.com