Inside MMA has reported that Strikeforce heavyweight champion Alistair Overeem has received a release letter from the promotion. Overeem, one of the original participants in the Strikeforce World Heavyweight Grand Prix, pulled out of the tournament after refusing to accept a bout date for the second leg of the tournament in September.

The champion claimed that Strikeforce had originally told him to be ready for an October or November date. After preparing to begin his camp at the start of August, in addition to an injured toe coming out of his fight with Fabricio Werdum, Overeem felt he wouldn't be ready to accept a date so close.

This comes on the heels of comments made this week by Scott Coker during an interview with AOL.com (transcribed by Cage Writer):

"I mean that's something we're going to sit down with his manager Bas [Boon] and have a conversation about," said Coker.
...
"We've been very good to Alistair. We've been very patient. It just didn't work out," Coker said. "If we could've took this fight to October or November we definitely would've done it."

The biggest question about this move is whether it signals Overeem's jump into the UFC or if it speaks to the relationship with Overeem's camp and Zuffa as a whole.

This is also a huge blow to Strikeforce's credibility as a promotion. They've lost two of their champions within the last few months, and their light heavyweight champion is about to move up in weight to take on their heavyweight jewel (however much luster he has lost) on Saturday night.

Update: The HDNet press release (via MMA Nation) provides some more details:

Also according to the source, Overeem has been dealing with more serious injuries than originally reported, including a broken toe and rib and elbow problems.

Video of the Inside MMA story after the jump.