Anthony Pettis out 7-8 weeks (knee)

Newly crowned UFC lightweight champion Anthony Pettis has been diagnosed with a sprained right knee, following an MRI the fighter underwent Tuesday.

The injury will require seven to eight weeks of rehabilitation, according to UFC president Dana White. In the meantime, Pettis can already start thinking about his next challenge -- a title defense against No. 1 contender TJ Grant.

"It's a [posterior cruciate ligament] sprain -- a Grade 2 sprain," White said on ESPN's "SportsCenter." "He's got [a lateral collateral ligament] strain, but there are no major tears and he will be back in seven to eight weeks.

"He'll have seven to eight weeks of therapy and then he will fight TJ Grant in his first defense."

Pettis (17-2) suffered the injury when he checked a kick during the first round of his championship win over Ben Henderson at UFC 164 last weekend in Milwaukee. He finished the contest via armbar at the 4:31 mark.

In Grant, he'll face the man he replaced at UFC 164. Grant (21-5) was originally scheduled to meet Henderson but withdrew in July due to a head injury. He earned the rank of No. 1 contender on the heels of a five-fight win streak.

No date or venue has been announced for the planned title bout.

The announcement cools talk of a potential fight between Pettis and current featherweight champion Jose Aldo, a matchup that was supposed to take place earlier this year but fell through due to another Pettis knee injury.

White said that if Pettis is successful in his first title defense, Aldo (23-1) could be next.

"[Aldo is a] 145-pounder but, obviously, that's the fight they both want," White said. "TJ Grant earned the shot; he gets the next shot. If Pettis defends the title and gets that win, we'll probably be looking at Aldo next."