UK's Alex Poythress tears ACL

LEXINGTON, Ky. -- Kentucky starting forward Alex Poythress will miss the rest of the season after tearing a knee ligament during practice in a devastating loss for the top-ranked Wildcats.

Coach John Caliparisaid Friday that Poythress was injured in practice Thursday on a breakaway layup without contact.A date for surgery has not been set, but recovery typically takes six to eight months.

"Things that people can't do, he can do -- and they all came at great times," Calipari said Friday as the Wildcats wrapped up preparations for Saturday's game against No. 21 North Carolina. "I can remember last year against Louisville his three-minute span was ridiculous. So now we don't have that guy that we can play poorly and he'll go do something that will get you back in the game."

On the emotional impact of losing Poythress, Calipari said: "'Next man up' and all that, it's all great coachspeak. The reality of it is, the fear and anxiety and all the other stuff that Alex has and we have for him, it zaps you."

Poythress' injury causes a major shake-up to Calipari's two-platoon system, in which the 6-foot-8 junior was averaging 5.5 points and 3.8 rebounds in 20 minutes of action.

"I don't want to throw kids to the wolves," Calipari said of how he'd adjust his platoons. "I don't want to do that to them, that's not fair. The only thing I can tell you is it will be with these players in mind. In other words, how do you give all the kids their opportunity yet how do you make this fair so the kids that are on the floor have a true chance of playing well because the guys on the court with them can do this. Some of this will just be throwing -- at some point let's try this lineup and see how they work."

Freshman guards Devin Booker and Tyler Ulis missed Wednesday's 56-46 victory over Columbia with unspecified injuries. Both players practiced Thursday, which means they will likely be available for Saturday's game against the Tar Heels, the latest of several big tests for a Wildcats team with national title aspirations.

And now Kentucky will be left to proceed without one of its key regulars.

"Our team was devastated for Alex when I told them," Calipari said. "There were tears throughout the room because this hurt them to the core. How they will respond I really don't know, but I will do my best to be there for each of these kids.

"I told them, this is a big blow to our team. No one will be able to replace Alex and what he did for this team. I go back to last year's NCAA tournament. Without Alex, we don't win those games. No one will be able to replace him, but now everybody has to do a little bit more as we try to circle the wagons."

Pursuing a title was a key motivation for Poythress to return for a third season with the Wildcats after last spring's NCAA title-game loss to Connecticut. Pictured on the front cover of this season's media guide with 7-foot fellow junior Willie Cauley-Stein, the two are the most experienced players on a 10-deep roster featuring nine Wildcats at least 6-6, leading Calipari to implement a two-platoon system.

"It just ruins our platoons a little bit or a lot," Cauley-Stein said. "No one can make the plays he makes, he's a freak athlete. He does special things that you can't really replace. So now we just have to figure out how to play differently."

The muscular Poythress was shooting just 38 percent from the field but leads Kentucky in free throw percentage at nearly 86 percent. His 12 blocks rank third on the team while his 30 rebounds rank sixth.

ESPN.com's C.L. Brown and The Associated Press contributed to this report.