Call me a shameless Jason Bergmann apologist, but I wonder if the root of his problems isn't his August 13 start against the Mets, when a chronically short-handed Manny Acta had little choice but to leave Bergmann in the game to allow 10 runs (6 earned) over 3 innings and throw a whopping 51 pitches in that fateful third inning. I wrote about it at the time as a risky move that could come back to haunt us.
Up to that point in the season, he had walked just 33 of the 479 batters (6.8%) he'd seen all year. That's a very good number. In his four starts since, he walked 10 of 90 (11.1%).
There's still a lot we don't know about the connection between usage and pitcher injury, but the data we have points to the basic principle that pitchers get hurt not so much from pitching a lot, but from pitching tired. That's why there's so much attention paid to pitch counts and innings counts. But a pitcher can also be at risk if he is asked to throw an unusually high number of pitches in a single inning. Fifty-one pitches is a huge number of pitches.
There hasn't been any suggestion that Bergmann is hurt, but he could be overly fatigued. It's entirely possible that he lost a measure of arm strength following that start, some of the life off his fastball. His velocity has been fine, with his fastball sitting around 89-90. In fact, in the August 30 game against Atlanta, his fastball was hitting 93 according the Gameday's Pitch F/X data.
But sometimes a gassed pitcher will try to throw harder in order to compensate for fatigue or injury, and usually the result is a loss of command. When a pitcher is "overthrowing" in this way, you often see their "front end open up," meaning a right-hander's left shoulder turns towards first base early so that the pitcher's chest faces the batter sooner. Again, the result is a reduction of command and also a reduction in the pitcher's ability to deceive the hitter, as the "opening up" often makes it easier for the hitter to recognize what's coming.
You can really see the difference in his mechanics if you look at the contrast between his last really good start, the seven-inning, one-run performance in Coors on August 7. Against the Rockies, you can see that his left shoulder stays pointed towards home plate and his arm moves forward with his body in a fluid, easy motion. But in these clips against Atlanta, his left shoulder is visibily opening up and his arm is way behind his head as his arm motion starts toward home plate.
This is more or less what St. Claire described as Bergmann's problem. (Incidentally, this was also what St. Claire diagnosed as Ayala's problem, after his command cratered following his stretch of overuse in April and May.)
I don't know that the 51-pitch third inning against the Mets is the cause of Bergmann's problem, but the circumstantial evidence suggests that this could be a factor. Certainly, that 10-run disaster at New York was the turning point for him.
Just something to consider before you decide that Bergmann, like Ayala, is a useless bum who should never again be on a mound for the Nationals.