BOSTON -- After being knocked around en route to a 7-4 loss to the Rays on Friday night, Red Sox pitcher Jon Lester was accountable. Disappointed by what he deemed an “unacceptable” performance, which wasted a chance for Boston to move above the .500 mark for the first time this season, he held only himself responsible for what went wrong.

Well, almost.

Based on his body language during the outing, and his answer to the first question asked of him afterward, one needn’t be sage in subtlety to realize Lester believed home plate umpire Mark Carlson bore some culpability, as well.

“I wasn’t good. I didn’t locate,” he responded. “I felt like I had to throw the ball in a keyhole.”

According to PitchFx data, Lester had a gripe. That charting said Carlson called balls on three pitches that were actually inside the strike zone — including two during a third-inning encounter with Carlos Pena, which accounted for balls three and four of what became a five-pitch walk.

Neither toss was even borderline, according to the computer. But what was worse than Carlson missing those calls was Lester’s reaction. After both pitches he glared toward the plate, his displeasure more than apparent and his focus clearly affected. It cost him a single to BJ Upton, and although he recovered to strikeout Luke Scott, Carlson missed another should-be-strike on Ben Zobrist — and Lester walked him, too. That loaded the bases.

Then, when the perturbed lefty grooved a 3-1 fastball right down the pipe, Matt Joyce unloaded the bags with the grand slam that sent Tampa on its way to a win.

Botched calls are part of the game. In fact, Carlson also missed three pitches that should’ve been strikes for Rays righty Alex Cobb — and maybe the most disappointing aspect of the situation from a Red Sox perspective was that the 24-year-old rookie call-up reacted better than the 28-year-old veteran in his seventh big-league season.

Once he was rattled, Lester lost his ability to dictate battles and started leaving meaty pitches over the heart of the plate. The result was two more taters on top of Joyce’s slam, and further evidence that Sox starters need to stop squabbling with the umpires and instead start focusing on executing the next pitch.

Manager Bobby Valentine made a mound visit earlier this season to deliver that message to Felix Doubront, but Boston’s veterans are even worse offenders. Josh Beckett was jawing with Bill Miller the day he gave up five homers in Detroit. As he’s struggled, Clay Buchholz has stared down an ump or two. Then Lester let the men in blue get to him Friday.

“Got squeezed on some big counts that we needed,” said catcher Jarrod Saltalamacchia, “...and they did a great job of hitting pitches whenever we missed.”

The former is going to happen. But letting it lead to the latter?

That is really what’s unacceptable.

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When Lester took the mound Friday, he did so as one of five pitchers in baseball who had completed multiple games this season. When he left the bump, though, he did so having amplified a developing concern about his ability to work deep into games.

By lasting just four innings — and seeing his earned run average climb to 4.72, while his record fell to 3-4 — Lester failed to deliver a pitch in the sixth inning for the sixth time in his 16 starts since the beginning of last September. By comparison, prior to this current stretch Lester had failed to reach the sixth inning just six times in his previous 82 starts. And one of those came in a game where he didn’t allow a hit, but was pulled after four frames because of an injury.

Also disturbing was that Lester allowed long balls in two consecutive plate appearances against lefties. That’s as many homers as the southpaw had allowed lefties over the previous calendar year.

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Valentine decided to sit Will Middlebrooks on Friday night, playing Kevin Youkilis at third base and Adrian Gonzalez at first. In order to get all three in the lineup at the same time, the manager implied that he’s comfortable with at least seeing what Gonzalez can do in Fenway’s spacious right field — but he also said he continues to wonder if there might be other ways to use Middlebrooks, as well.

“I keep asking if there’s another position, and I keep hearing, ‘No,’” Valentine said. “Other than DH, I’m not sure what that would be. We have experimented with some things, so I wouldn’t say it’s out of the realm of possibility — but it hasn’t been discussed in a light that has inspired me.”

To this point, however, any conversation of what Middlebrooks might be able to do has been restricted to management. In an effort to keep the rookie’s attention attuned properly, Valentine hasn’t asked the player directly if he could play a position other than third base.

“I’m trying to make sure that a young player is concentrating on what he should be concentrating on,” the manager said, “and he’s doing a pretty good job of that.”

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Today is New Hampshire Day at Fenway Park, where the Red Sox Foundation will present $1,000 scholarships to 35 college-bound students from across the Granite State. It’s the biggest group of honorees the program has ever awarded, with recipients selected based on academic performance, financial aid eligibility and community service.

Coincidentally, but humorously, the Sox announced Molly Whitaker as the scholarship winner from “Leganon” High School, misspelling, of all places, “Lebanon” — the school that produced the club’s own general manager, Ben Cherington.

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STAT OF THE WEEK: Entering Saturday, the Sox were 19-9 in games when they hit a home run. They were just 3-14 when they didn’t.

Dave D’Onofrio covers the Red Sox for the New Hampshire Union Leader and Sunday News. His e-mail address is ddonof13@gmail.com.