Twins manager Ron Gardenhire was in the clubhouse talking to his starter, Kevin Correia, during the play.
"I actually was looking at the TV, and I took off running as soon as I saw, 'double,'" Gardenhire said. "I sprinted right out of the clubhouse. I had to push a couple guys out of the way to get on the field."
It took only a moment before crew chief Dana DeMuth emerged with the correct call: home run.
Hernandez was involved in a much higher-profile dispute May 8 in Cleveland, where he was crew chief for an A's-Indians game. Oakland's Adam Rosales hit what replays showed was a tying home run in the ninth inning, but umpires ruled it a double on the field and stuck with that ruling after reviewing a replay. The A's lost, 4-3.
Mauer's homer was the second implementation of replay review at Miller Park this season. The umps also conferred on April 30 and overturned a call, resulting in a home run for Pirates outfielder Starling Marte.
Adam McCalvy is a reporter for MLB.com. Follow him on Twitter at @AdamMcCalvy. This story was not subject to the approval of Major League Baseball or its clubs.