After striking out Ryan Garko with two runners on base to end the third inning, Hernandez jogged to the dugout, turned and pointed at Buck and began yelling. The two players charged each other and began throwing punches before being separated by teammates and coaches.
"Nothing happened," Hernandez insisted despite being told the skirmish was shown on television. "Everything's cool. Let's talk about the game. This was a good win. I thank my teammates for doing a good job."
Hernandez allowed three hits and one run over the first three innings and was helped by two double plays. In the third, left fielder Esteban German caught a drive by Cleveland's Andy Marte with his back against the wall and center fielder David DeJesus made a catch against the wall in right-center on a ball hit by Grady Sizemore.
The right-hander then gave up a single to Jason Michaels and walked Victor Martinez before fanning Garko.
Hernandez and Buck both came back out onto the field for the bottom of the fourth.
"It's September and there was some sort of misunderstanding," Royals manager Buddy Bell said. "Something was said and both guys are extremely competitive, but they have to have a little more poise. We met and straightened things out."
Buck was unavailable for comment.