The Wildcats made only two field goals over the final 13 minutes of play, watching a nine-point lead vanish in a 67-62 loss to the Bears at AT&T Stadium in Arlington.
Third-ranked Kentucky (7-2) also turned the ball over five times and missed five of 11 free throws during that fateful stretch as No. 20 Baylor (8-1) gradually pulled away.
The Bears became the first team to outrebound UK this season, dominating the glass 41-25. Rico Gathers came off the Baylor bench to grab a game-high 13 rebounds in only 22 minutes of play. Cory Jefferson added eight for the winners.
"The key plays were the rebounds down the stretch," Calipari said. "There were three or four, we get those, we win the game. (But) it wasn't that important. It was more important that (the players) get the ball on offense. That's where we are as a team right now. But that's what you would expect from a young team. I would hope they have more fight to win the game… They didn't."
Kentucky trailed by nine points early in the game, but battled back to lead 38-35 on the strength of 11 points by Aaron Harrison at the break.
The Wildcats picked up where they left off in the second half, building a 46-37 lead after a pair of Julius Randle free throws at the 15:52 remaining. The UK lead teetered between seven and nine points the next three-plus minutes until a Randle dunk at the 13:07 mark made it 50-41.
That would be UK's last basket until a James Young 3-pointer at the 9:38 mark.
And that would be UK's last basket until a James Young 3-pointer with 3:05 to play.
The Cats made no field goals over the final three minutes and missed four of their six free throws. They finished 12 of 23 at the line, but Calipari was more concerned about the effort than the shooting woes.
"Our fans just want to see a team fight and battle and compete, and this team didn't," he said. "As soon as this thing got rough and the first two raindrops hit, it's like a front-running team, the raindrops hit, we stop fighting. We start looking for excuses with the heads down. That's what we are right now. But we know that, and that's why we have to play these kind of teams."
Randle led Kentucky with 16 points and eight rebounds. Aaron Harrison followed with 15 points and six assists. James Young added 14 points for the Cats.
Junior college transfer guard Kenny Chery paced Baylor with 18 points, many coming off a high pick-and-roll play that confounded the UK defense throughout the game. Isaiah Austin and Jefferson each added 13 for the Bears, who beat the Cats for the second year in a row.
The teams played to a crowd of 12,818 who braved the ice and snow in the greater Dallas area to make it to the cavernous 100,000-seat stadium, home of the NFL's Cowboys.