BOSTON — For the last two weeks, Jason Varitek’s batting average has dipped almost as sharply as the price of gas has escalated.

He endured a hitless streak covering 24 at-bats, the longest of his career, and when he came to the plate in the eighth inning last night, he could claim only four hits in his last 47 at-bats, a far-from robust .091 batting average.

It’s frequently said about Varitek that his main contribution comes from behind — not at — the plate and that any offense he provides is purely a bonus. But this was getting ridiculous.

Varitek had become almost an automatic out, so much so that there was some surprise that, with first base open, two on and two out, Arizona manager Bob Melvin didn’t elect to intentionally walk Mike Lowell to get to Varitek.

(Melvin later confessed that he pitched to the Red Sox captain only because he feared the Red Sox would pinch-hit Kevin Youkilis for Brandon Moss, due next, with the bases loaded.)

Instead, Lowell laced a two-run Wall double, tying the game at 4-4. Varitek then followed with a line single to right, scoring Lowell with the go-ahead run.

Varitek isn’t one to show his emotions often, but after the Red Sox had edged the Diamondbacks, he hinted that the frustration had been building.

It didn’t help that in the first inning, with two on and no out, he had scalded a ball up the middle that looked to be a run-scoring single. Instead, the ball caught Arizona starter Doug Davis, caromed directly to shortstop Stephen Drew and resulted in an inning-ending groundout.

“I think if (right fielder Jeff Salazar) had caught (the single in the eighth),” said a smiling Varitek, “I would have exited the field, come up here, dressed and gone home.”

Instead, the ball fell in, Lowell scored and Varitek was the unlikely offensive hero.

The slump had been building for a while, long enough so that when a radio reporter gently inquired about the catcher’s struggles “the last few days,” Varitek corrected him.

“It hasn’t been the last few days,” said Varitek, in a bit of self-effacement. “It’s been the last few weeks.”

There had been some positive signs of late. There was the Wall double Monday night, one of just two hits off Dan Haren. And over the weekend, there were some hard-hit lineouts that offered hope.

“When you haven’t hit .300 (in a season),” said Varitek, a smile again sneaking across his face, “you learn to take those as hits.”

Outs on the scorecard, but moral victories for a struggling hitter, it was suggested. Varitek nodded in agreement.

The catcher had been working with hitting coach Dave Magadan of late, trying to fine-tune his approach at the plate. Sometimes, his swing gets too long and Varitek needs to remind himself to keep it more compact, to keep his approach more simple.

But just finding time to work on hitting can be a challenge. Scattered around Varitek’s locker last night were a handful of notebook binders, all of them filled with detailed scouting reports on recent opponents.

Since the Sox are in the midst of interleague play, there’s been more to study about National League hitters and less time to work in the cage.

“We do our work every day with Mags, regardless,” shrugged Varitek, who won’t take cover behind excuses. “We’ve been working all year.”

Varitek has been making adjustments, trying to get his bat through the hitting zone quicker. But the results take time.

“That’s what’s frustrating — when you see a pitch and know the bat should be there, but it isn’t,” said Varitek.

It doesn’t help that Varitek is a switch-hitter, with different approaches from each side of the plate. Factor in his workload as the team’s starting catcher and he has half the time to do twice the amount of work.

At times, his offense suffers and his slumping average – just .231 for the season going into last night – reflects the disrepair in his swing.

But you’d never know it from his attitude.

“We talked about it the other night,” said manager Terry Francona. “When he’s not swinging, you’d never know it by his demeanor. As long as we win, he’s the same. But that was a big hit. Not just for the team, but for him. That’s good.”

For one night, at least, Varitek’s contribution at the plate wasn’t just a bonus in a Red Sox win; it was essential.

smcadam@projo.com