Felix DoubrontBOSTON — It might not be long before Felix Doubront starts navigating uncharted waters. He better patch up his ship, or else it could be a choppy ride.

Doubront lasted just four innings and was touched up in Friday’s 10-3 loss to the Yankees. It’s the second subpar start in a row for the left-hander after he was arguably the Red Sox’ most consistent starter for 2 1/2 months. If all goes according to plan, Doubront will soon reach a new career high for innings pitched. While that certainly speaks to his solid season, it also raises questions about whether Doubront is built to withstand the wear and tear of a heavy workload.

Doubront has now made 23 starts and thrown 132 innings. In 2012, Doubront made 29 starts and threw 161 innings, although it was right around this time last season that he broke down a bit.

Following his 22nd start of 2012, Doubront went on the disabled list with what was described as a knee injury. It was clear, however, that he was also fatigued, so the DL stint was really a way to shut him down and give him some rest. Doubront and the Red Sox don’t have such a luxury this season — they’re contending this time around — so the southpaw’s two-start skid is somewhat concerning.

Doubront lasted just four innings in Kansas City last Saturday. He gave up three runs on six hits and four walks while looking like the early-season version of Doubront, who walked a tightrope just about every time he took the hill. Friday’s start against the Yankees was even worse, as Doubront gave up a career-high seven runs (six earned) on eight hits.

Neither manager John Farrell nor Doubront seems too concerned about the lefty wearing down as the season rolls on, even if the elephant is knocking on the door and looking to enter the room. Instead, they feel that the struggles over Doubront’s last two starts are simply a matter of lack of execution.

“It’s been location,” Farrell said. “Where he’s been more consistent [he’s been] down in the strike zone and particularly to some right-handers with his fastball command to his arm side away to them. If you pinpoint one thing, it’s been location overall.”

Doubront missed with several pitches Friday, including two to Mark Reynolds and Alfonso Soriano. Reynolds lifted an 0-2 changeup into the Monster seats for a two-run homer in the second inning, and Soriano jumped on a 1-1 fastball for a three-run shot in the third inning. At that point, it was all over but the shouting.

“Mislocation on a few pitches. Two swings cost us five runs,” Farrell said. “More than anything, [it was] just difficulty repeating in the bottom of the strike zone. The last time he pitched here against Arizona, he was outstanding in the bottom of the zone and the last two times out, it’s been where he’s missed up on the plate and he’s had to pay for it.”

Doubront is still in the midst of a solid season. He strung together 16 consecutive starts allowing three earned runs or fewer, and he went from a wild card to one of Boston’s most reliable pitchers. That’s a good reason to be optimistic, but it’s also why he needs to break out the tool box and fix things up before September arrives.

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