BALTIMORE — What’s wrong with Daisuke Matsuzaka?

Has he hit the wall in the major leagues? If it’s not fatigue, is there something physically wrong with him?

How else to explain Matsuzaka’s dreadful performance last night when the woeful Baltimore Orioles, losers of 15 of their last 17 overall and a franchise-record-tying 11 straight at home, battered the right-hander for eight earned runs on six hits in only 2 2/3 innings at Camden Yards, a game the Boston Red Sox lost, 11-5.

Included in that ugly line were two gopher balls, a solo shot in the first by light-hitting Tike Redman, who began the year playing ball in Japan, and a grand slam by Scott Moore, a veteran of only 53 big-league at-bats before unloading on a fat fastball for his first hit in 14 at-bats in the majors this year.

Moore’s slam capped a seven-run third-inning explosion at the expense of Matsuzaka, who had been handed early leads of 2-0 and 4-1. As the ball disappeared into the bleachers, well past Coco Crisp’s vain attempt at a leaping catch, Dice-K put his hands on his knees and bent over in frustration and irritation, and a few seconds later he was yanked by Boston manager Terry Francona.

The start was by far the shortest of the season for Matsuzaka, who had gone at least five innings in each of his previous 28 outings.

His fastball had little life or movement. His slider had precious little movement or bite. And in the seven-run third, Matsuzaka was missing consistently up and away with fastballs to left-handers and tried to navigate his way through the jam by using just fastballs and sliders, a plan that clearly didn’t work.

What makes last night’s horror show more distressing is that it cannot be shrugged off as an isolated, one-of-those-games kind of outings. It continued a downward spiral for the former Japanese League star, for whom the Red Sox paid more than $100 million to secure his rights and sign him to a contract last winter.

The postseason is around the corner, and Dice-K is faltering badly down the stretch.

Over his last three starts, Matsuzaka is 1-2 with a 12.56 earned-run average, having been strafed for 22 hits and 20 earned runs in only 14 1/3 innings. And over his last five starts, Dice-K is 1-4 with a 9.57 ERA, tagged for 32 hits and 28 earned runs in 26 1/3 innings.

Not surprisingly, the Red Sox’ explanation for last night’s disaster did not offer up excuse or injury as a reason.

Francona, for instance, said that he was one pitch away from getting out of the third inning with the game tied at 4-4 and going back to the mound for the fourth. Moore, though, blasted that “one pitch,” a 94-mph fastball that sat on a tee for him, thigh high, down the middle.

“A slump? I don’t think it matters what I call it. What he did five starts ago doesn’t have any bearing (on last night’s outing),” said Francona. “In that big inning it seemed like especially the command of his fastball just kind of abandoned him.”

Pitching coach John Farrell talked about Matsuzaka’s habit of trying to power his way through trouble, not using his curveball or changeup in such situations.

“I don’t think it’s physical,” said Farrell. “When he gets in a big inning like that he has a tendency to rely solely on his fastball and when he does that he sacrifices location. He was 40 pitches into the inning and he was still throwing 90 miles an hour. That’s a testament to his strength, but at the same time, any pitcher will lose sink or life (on the pitch) when he tries to muscle up and throw it too hard and I think that was the case tonight.”

Matsuzaka, meanwhile, apologized for being the pitcher to drag down the team (the Sox, who are 29 games over .500, are only 15-14 when Dice-K starts).

“I can’t really use fatigue as an excuse for myself,” said Matsuzaka, who took a 10-1 lead into the sixth in his last start but ultimately was charged with seven earned runs in 5 1/3 innings against the Blue Jays.

“I think all of use are having to fight hard this season. At this part of the season fatigue affects everyone. I had an inability to throw strikes tonight,” said Matsuzaka.

Still, it wouldn’t be a stretch to guess that maybe he is getting tired, worn down by the season, which is longer here than it is in Japan and features much more travel.

The Sox have tried to give him extra rest between starts — as they try to do with everyone in the rotation. Over his last five starts, for instance, he worked on at least an extra day of rest three times.

In his last two seasons in Japan, Matsuzaka pitched 215 innings in 28 games in 2005 and 186 1/3 innings in 25 games in 2006. This season, Masuzaka has made 29 starts already, totaling 184 1/3 innings, and it’s only Sept. 9.

skrasner@projo.com