One was obvious, a two-run homer to Brooks Conrad in the fifth that ultimately was the difference in the Orioles' 3-1 loss to Tampa Bay.
"That's the big mistake I made today. I think that's the first and only mistake I make today," said Chen through interpreter Tim Lin. "I wanted to throw a slider. I had been able to locate a slider well today. And that was higher (than I wanted) and he hit it well."
The other mistake? Well, maybe it was a phantom one. That's not how second base umpire Gary Darling saw it. And that's really all that mattered.
With no outs and B.J. Upton on first, Chen was called for a balk, allowing Upton to get to second base. Upton advanced to third on a sacrifice bunt and scored the insurance run on Jeff Keppinger's single.
After the game, Chen, who gave up three runs on four hits and three walks and struck out five in 6 2/3 innings, still was not sure what he did wrong.
"To be honest with you I have no idea. I have a standard routine when I was on the mound and I do the same routine every time. After the game I went back to the video room and I keep checking. I watched it (over and over). I couldn't get it and to be honest with you I don't understand that."
Buck Showalter wasn't happy with the call at the time or afterward, saying Chen simply wiped his pants' leg and should have been fine.
"He was wiping his hand on his leg," Showalter said. "Three guys saw it and one guy just over-umpired it and called it a balk."
Showalter gave Chen credit for handling the call -- though Chen was obviously frustrated.
"He should have (been), but I thought he held it pretty good after the fact," Showalter said. "I think everybody was (frustrated). He's competitive. I think some people miss that about him. This guy likes to compete. He really likes to win."
Chen said he wasn't pleased with how he dealt with the adversity.