Crisp smashed an offering from Royals starter Luke Hochevar that appeared to hit somewhere around the top of the right-field wall and bounced back to right fielder Jeff Francoeur. Crisp pulled up at second base with a double.
A's manager Bob Melvin came out to talk with second-base umpire Paul Nauert, and, following the conversation, the umpires ran in to take a look at the replay. After a short review, the hit was ruled a home run.
Video replays showed that the ball did appear to land behind the top of the outfield wall and bounce back into play, which is a home run at Kauffman Stadium.
"I thought I saw it skip off those bars out there, and that's a home run," Melvin said. "For me, if it hits the pad and comes back, it's pretty easy to see that. It looked like it came up and skipped of the bars."
The review was a big one, as it broke a scoreless tie and ended up being the winning hit. Hochevar had been dominating the A's hitters and Crisp's solo shot was just the second hit of the night for Oakland.
"It felt like we were starting to grind a little harder than we should. You start digging, and it just doesn't feel like anything's going to happen," Melvin said. "That was, at the time, certainly the key hit of the game, and it ended up being the key hit."
Yoenis Cespedes followed in the seventh with a no-doubter into the left-field seats.
The review was the eighth in Kauffman Stadium history and the second to be reversed. Billy Butler's walk-off homer against the Angels, originally ruled a double, was changed on June 1, 2011.
Thursday's review was the second replay of the season at the Royals' home digs. On Aug. 1, Cleveland's Carlos Santana hit a home run that was upheld.
Vinnie Duber is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.