The trip wasn't meant for Rondon. It was meant for the Royals' Alex Rios standing at second base.
"I just stared at him," McCann said on Friday afternoon. "Not knowing if he was really [stealing signs] or not, but my job is to make sure it didn't continue if it was happening."
Though other players on the field can look and try to get an idea, sign-stealing is usually up to the catcher to track. It could be the look a baserunner gives as he takes a lead off second base, or the slight movement of a hand, or anything that might be construed as a signal to the batter.
Stealing signs is not a rarity, though manager Brad Ausmus said it didn't happen often during his playing days. When it does happen, it's often with a small group of players, usually veterans, rather than a teamwide thing. Those who did so often picked up reputations.
"I don't know that I ever got a sign from second my entire career," Ausmus said.
Past Tigers catchers, such as Brandon Inge, used to downplay the practice, saying it was on the catcher to change signs. McCann wasn't going to make a huge deal of it, but in that situation, with the Tigers trying to hold onto a lead in the ninth, he was going to shut it down.
"If you can relay signs and get away with it, good for you," McCann said. "But if you get caught ... Was he doing it? I have my suspicions. No one will ever know except for him. But I do know he wasn't able to relay them beyond that trip to the mound."
And that was the point.
"I don't know if Mac knew for sure he was doing it," Ausmus said. "I think he was just making him aware that he's watching him. If a runner knows that the catcher's kind of focusing on them and they're stealing signs, there's a good chance they'll back off."
Jason Beck is a reporter for MLB.com. Read Beck's Blog, follow him on Twitter @beckjason and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.