Red Sox starter Josh Beckett, delivering a first-inning pitch against the Blue Jays yesterday, was the victim of a third straight leaky performance by the bullpen.

AP / J.P. Moczulski

TORONTO — All eyes were on Josh Beckett as the Boston Red Sox’ ace made his disabled-list-delayed 2008 debut yesterday at Rogers Centre.

And while the right-hander was OK, tiring in his fifth and final inning as he surpassed the 75-80 pitch count he was expected to throw, by the middle of the game the Red Sox’ focus was on a third straight leaky performance by the bullpen, specifically the middle relievers.

This time the culprit was Manny Delcarmen, who, for the second time in the series, lost a key battle with Blue Jays designated hitter Frank Thomas.

Delcarmen, stung for a tie-breaking two-run double on a changeup in a Friday night setback, went with a 95-mph fastball for his first pitch to Thomas yesterday.

But he badly missed his location, the ball running across the inner half of the plate, just above the knee, and Thomas crushed it to left-center for a tie-breaking grand slam that propelled Toronto to a 7-4 victory and a three-game sweep of the weary Red Sox.

The blast tacked on three more runs to Beckett’s line, not to mention a loss, as Boston, now 3-4, plunged into the American League East basement.

“I was aiming down and away, and when I threw it, I thought it was good,” said Delcarmen. “Then, all of a sudden, it moved over the middle of the plate. I don’t know how it ended up there. [Thomas] has had my number the last few times I’ve thrown.”

Beckett, who gave up a two-run homer on a hanging curveball to Vernon Wells in the fourth, retired the first two batters in the fifth, on seven pitches. But then he gave up a broken-bat single to Aaron Hill and walked Alex Rios and Wells, filling the bases, running his pitch count to 92 and forcing manager Terry Francona to lift him.

Beckett was barely to the bench before Thomas launched his 11th career grand slam, turning a 2-2 nail-biter into a 6-2 Toronto advantage that no doubt had the already mentally weary Red Sox longing for their greatly anticipated journey back to Boston after a 19-day road trip that had taken them to Japan, the West Coast and Canada.

The Sox, to their credit, did try to scratch their way back into the game, bringing the tying run to the plate with one out in the ninth.

But Jeremy Accardo held on for the save, preserving a victory for Toronto’s ace right-hande, Roy Halladay.

“I thought (Beckett’s) legs started to go,” said Francona. “That’s understandable. We wanted him to get through five. He deserved it. Everything he threw early in the game was knee-high with good velocity. But you don’t want to go too long with him (in a first outing).”

Beckett didn’t seem impressed or depressed by his performance.

“I felt good health-wise, but it’s not the result you want,” said an impassive Beckett, who was slowed early in spring training because of a lower back strain. “(I felt) just some normal fatigue, nothing I’m not used to. Just need to work on some things, the normal day-to-day stuff between starts.”

Catcher Jason Varitek’s critique was positive.

“He was good,” said Varitek. “He was just missing (in the fifth). If that means he was tired, I’m not sure.”

While everyone on the Sox was hoping to get some rest today, a day off in the schedule in advance of tomorrow’s Opening Day game against Detroit, the faltering relief corps had to be a cause for concern for the team’s brass, even if the season is only seven games old.

Not setup man Hideki Okajima nor closer Jonathan Papelbon. They didn’t make it into a game in Toronto under their normal meaningful circumstances, and that was because the bullpen “bridge” collapsed each night before it could get to the dynamic duo.

Excluding the get-some-work-in inning apiece thrown by Okajima and Papelbon yesterday, the bullpen totals for the three games were ghastly — 6 1/3 innings, 11 hits, 11 runs, 10 earned runs, 5 walks, 4 strikeouts.

On Friday, Francona went to his bullpen with the game tied at 2-2 in the seventh inning. There were runners at third (walk by David Aardsma) and first (single off Javier Lopez) with none out. Delcarmen notched the first two outs on foul popups to first, but Thomas laced the clutch two-run double, and Delcarmen was nicked for another run in the eighth in a 6-3 loss.

On Saturday, Francona went to the bullpen in the sixth with the Sox down, 4-2. By inning’s end, it was a 10-2 deficit. Kyle Snyder (two walks) and Bryan Corey (four hits, including a two-run homer by Thomas) relegated that game to the loss column.

And then there was yesterday’s contest.

On the first pitch from the relief corps, the Sox went from a 2-2 tie to a 6-2 deficit at Delcarmen’s expense. And the Jays tacked on an unearned insurance run against Aardsma before Okajima and Papelbon took over.

Okajima worked around one of Julio Lugo’s three errors in a scoreless seventh, and Papelbon whiffed all three batters he faced in the eighth, but by then, as had happened in the previous two games in Toronto, the game had been lost by the middle relievers.

skrasner@projo.com