In the fifth inning of that game vs. the Red Sox, Shane Victorino hit a shot back up through the middle that nearly hit McCarthy.
"The ball that Victorino hit back at me kind of [messed] me up," McCarthy said. "I don't feel like I take it out to the mound with me, but that was the first time I was really shaken after something."
It came a couple of months after McCarthy suffered a seizure while out to dinner with his wife, Amanda. The seizure was related to the head trauma he suffered last year.
"You do as much as you can to forget and move and move and move and move, but for that [Victorino's liner] to happen coming off the DL, with the seizure and you're on medication and all of a sudden these things become very real again," McCarthy said. "That happens, and you realize you're that close away again, without being able to feel like I have any protection. We're not there yet with a [protective] hat. It's just trying as much as you can to get past it, get past it, get past it and just take the [darn] ball and go out and throw. I think it still exists in there, I just don't know to what extent it does."
McCarthy speculated that his mechanical issue of flying open -- pulling his glove away from his body as his arm comes forward -- could be in an effort to protect himself on the mound.
That prevents McCarthy from finishing his pitches in a strong position and could explain why his cutter has not been an effective pitch for him lately.
The D-backs hope McCarthy figures it out soon, because they can ill afford another disaster like Wednesday night -- when he allowed seven runs and lasted just 2 1/3 innings.
"I don't know if it's as much mechanical as he thinks it is," Arizona manager Kirk Gibson said. "I saw him throw two pitches to [Reds catcher Devin] Mesoraco, just wipe out. How many balls did you see those guys swing over the top of sinkers down and in? How many balls did they hit off their foot [Wednesday] night? Pretty simple, what you want to go with in my mind. He's been throwing his cutter a lot, and I don't think it's a great pitch for him. He's not consistent with it."
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.