Those concerns are magnified as the nation's top scoring team, Boise State, brings an 8-0 record to Rupp Arena tonight.
"They shoot 3s at a high clip, they run the dribble drive better than we run it, and they spread the court with four guards," Calipari said of the Broncos. "They have four guards, so somebody is going to have to guard a guard who is not used to guarding a guard. It's just how it is."
That's a scary proposition when Kentucky's perimeter defense has been the weakest aspect of the unit to date. In both of their two losses this season, the Wildcats have been carved up by the smaller, quicker guards. Michigan State's Keith Appling and Gary Harris combined for 42 points against UK, and Baylor's Kenny Chery worked off a high screen all night long en route to 18 points.
The lapses against Baylor occurred just five days after the young Cats were seemingly hitting their stride in a 79-65 win over Providence in which the Friars shot just 31 percent.
Asked Monday if he believed the Cats have the ability to be a good defensive team, Calipari said: "We need to be. I don't have any other thoughts, but we need to be a great defensive team. We don't have team confidence right now. The reason is because they are not relying on one another. They are not talking to one another, and we are not a great defensive team.
"When you become a great defensive team and rebounding team, you take great pride in it. We are not taking great pride."
The UK boss wants better on-ball defense from all of his perimeter players, but he directly challenged freshman point guard Andrew Harrison to put more focus on that aspect of his game.
"It starts with your point guard," Calipari said. "If he can't pressure the ball, then somebody else has to be playing. It's just how it is."
Kentucky has only 36 steals as a team despite putting one of the longest teams in the country on the court. In the Baylor loss, the Wildcats failed to record a steal, the first time that has occurred since Calipari arrived in Lexington in 2009.
"There is not enough pressure on the ball, which is the main reason," Calipari said.
But he was quick to add that he's not overly concerned about the steals column. "It's not how I coach. We're not trying to steal every ball, but we do want pressure on the ball." His teams will typically have only a handful of steals, but a higher number of blocked and/or challenged shots leading to transition scoring opportunities.
"My teams historically have been low in steals," Calipari said. "I'm just saying, so what's the difference between three and zero or four and zero? You're not talking a big number.
"My teams are always high in blocks, so when they say turnovers to baskets, they never include a block, so you don't really get the true gist of how many blocks did we get and how many run outs did we get from there."
To that end, Calipari would like to see more of his big men contributing to defense than just sophomore center Willie Cauley-Stein, who owns 34 of UK's 68 blocked shots this season.
"Is Willie (Cauley-Stein) really the only guy who is going to block shots?" Calipari said. "Some guys just stand there and (say) I'm not involved in this."