Hayes, a 6-foot-7 forward who emerged as Wisconsin's top bench player this season, was saddled with early foul trouble in Saturday's contest and finished with two points and no rebounds in a season-low seven minutes.
"I didn't play well at all, which is the reason why we lost," Hayes said following Wisconsin's 74-73 loss, according to the Milwaukee Journal Sentinel. "I said this earlier in the year -- especially playing against good teams, I need to play well in order for us to win.
"I didn't do that today, and we lost."
Hayes was whistled for his second foul with just over nine minutes remaining in the first half and went to the bench.
"I went in there and got two early fouls and didn't play the whole first half," said Hayes, who claimed he was most disappointed with his defensive performance against Kentucky.
The Wildcats, who advanced to the national championship game for the second time in the last three seasons, shot 50 percent from the floor Saturday and outrebounded the Badgers, 32-27.
Hayes had enjoyed a productive stretch during Wisconsin's run to the Final Four, averaging 6.5 points and 3.5 rebounds in the Badgers' first four NCAA tournament games. But he attempted just two shots in Saturday's loss.
"I'm already coming off the bench," Hayes said. "So I wasn't able to get into a rhythm or get a feel for the game or what was going on out there.
"I wasn't able to get going. I guess you guys can blame it on me being a freshman."