The Red Sox will assess whether to shut down Felix Doubront (AP)

Through the first three-plus months of the season, a compelling case can be made that the season put together by Felix Doubront was the most significant development for the short- and long-term fortunes of the Red Sox. The 24-year-old left-hander laid claim to a spot in the rotation in spring training and positioned himself as a potential long-term rotation fixture by mid-July.

Through 18 starts, Doubront was 10-4 with a 4.24 ERA while striking out nearly a batter an inning (99 punchouts in 102 innings). His swing-and-miss rate was among the best in the American League, thanks to a diverse array – a low- to mid-90s fastball with sink, a cutter, curve and changeup. At times, he showed the ability to dominate opposing lineups, and he was demonstrating an improving ability to work deep into games, logging at least six innings in five of six and eight out of 10 outings through July 18.

But since he allowed one run in six innings against the White Sox that day, his season has gone in a dramatically different direction. And now, it seems fair to wonder whether it’s nearing a slightly premature end.

Doubront suffered the loss in the Sox’ 7-5 defeat at the hands of the Blue Jays on Friday. He gave up five runs on six hits (including a pair of homers) in four innings — his fifth straight outing in which he’s given up four or more earned runs. In his last seven starts since July 23 — a period that included a two-week stint on the DL to rest his shoulder — Doubront is now 0-4 with an 8.27 ERA. He’s worked five or fewer innings in five straight starts. Indeed, his run of five straight starts of five or fewer innings and four or more runs allowed is the longest such streak by any Red Sox pitcher since at least 1918 (thanks, baseball-reference.com!).

The left-hander is now at a career-high 134 2/3 innings, surpassing his previous career standard of 129 1/3 in 2008. This workload comes after injuries limited him to just 87 2/3 innings between the majors and minors in 2011 and 105 combined innings in 2010.

“His stuff’s pretty good,” suggested manager Bobby Valentine. “First run of the game, jammed all four hitters, gave up a run. The two-run inning, he got the first two guys out, nine pitches. He just kind of lost concentration. I think the stuff’s all right. He says his arm is fine. Just got to bust through the middle innings there.”

The fact that Doubront consistently has remained unable to accomplish that goal lends itself to the question of whether — despite still having stuff — his ability to locate and execute has been impaired by fatigue. Asked if the Sox might consider shutting him down given the diminished performance, Valentine did not rule out the possibility.

“We’ll discuss it,” he said.

If the Sox do decide to end Doubront’s year, the decision would come with the pitcher armed with a 10-8 record, 5.21 ERA and 136 strikeouts (against 58 walks) in 134 2/3 innings. He is one of just 14 big league pitchers to have more than a strikeout per inning this year (min. 100 innings), suggesting considerable stuff, but for now, the talent has stopped translating into the same impressive results that made his early season so promising.