Sounds like it. From this blog post, which also has some great stats on Fidrych’s heavy usage in 1976 and his strong deferred start to 1977:
https://prestonjg.wordpress.com/2016/03/26/update-things-i-meant-to-write-just-after-mark-fidrych-died/
“He threw complete games in seven of his first eight starts. By that time he was 6-2 with a 1.83 ERA. He didn’t give up a home run in his first 66-1/3 innings. He faced 38 batters in each of those last two starts, with just three days rest between them. Performance-wise, he was every bit the pitcher he was in 1976 (at least through the end of August), if not better”.
“Then he got the hell beat out of him in two starts, being knocked out in the sixth inning of each game, allowing 21 hits and 12 earned runs in 11-1/3 innings. He later came to believe he tore his right rotator cuff in the first of those two games, July 4 at Baltimore, although the injury wasn’t diagnosed as such until 1985. (In the 1986 SI piece, Gary Smith wrote Fidrych’s right shoulder popped “ten days after he returned from the disabled list,” which would be early June, which seems unlikely based on his performance.) On July 12 he was pulled while facing the fourth batter of the game and was done for the year. (Jim Crawford came in to relieve Fidrych and threw 8-1/3 shutout innings.) According to the next day’s Detroit Free Press, team doctor Clarence Livingood diagnosed Fidrych’s problem as “a tired arm.”