For the better part of the last year, Alfredo Aceves has represented a delicate challenge for the Red Sox.

Until now, the Sox have decided that the positives -- his durability, his versatility -- have outweighed the negatives.

But Tuesday night may represent a tipping point of sorts.

It was bad enough Aceves allowed eight runs on seven hits in 3 2/3 innings in a brutal 13-0 loss to the Oakland A's in 42-degree drizzle at Fenway Park. It was made worse by Aceves' actions in the third, when a) he threw 42 pitches, as he allowed six runs; b) balked twice in the span of a few hitters; c) failed to cover first base in time on a ground ball to the right side that would have ended the inning with the score only 3-0, and d) after the runner, Josh Reddick, was ruled safe, turned and made a lazy, flat-footed throw to the plate that sailed past catcher Jarod Saltalamacchia and allowed another run to score.

And when Aceves offered a litany of excuses for his outing -- blaming the weather conditions and the strike zone of plate umpire Hunter Wendelstedt, which he hinted was smaller for him than for Oakland starter Bartolo Colon -- and followed that by asking rhetorically of his teammates, "Why didn't we hit?'', he may have crossed a line.

"I don't know if I'd go into the effort level,'' said manager John Farrell. "[But there] seemed to be a lack of focus, given the way Alfredo has pitched this year for us . . . It wasn't a good night.''

Asked if it's become difficult to know what to expect from the mercurial pitcher from one outing to the next, Farrell was equally blunt: "It's varied - I will say that. He's healthy, he's got the ability to manipulate the baseball, as we've seen. You'd like to think that there'd be more of a known commodity in a given role, particularly in a starting role, when you've got five days to prepare for the next outing.

"Tonight wasn't one of his better performances.''