EXCLUSIVE: Lethal Weapon yesterday scored a dramatic, eleventh-hour Season 3 renewal by Fox with Seann William Scott replacing original co-lead Clayne Crawford. And this morning, Lethal Weapon was on the fall Fox schedule, retuning to Tuesday night.

No episode count was announced but I hear that, despite the fact that Lethal Weapon‘s third season is premiering in the fall, its order is for 13 episodes, not the standard full-season 22.

Besides sophomore shows that had debuted in midseason, whose initial Season 2 order is for 13 episodes, returning series on the fall schedule normally get full-season orders unless they are designed as limited runs, which Lethal Weapon is not. (Its first season consisted of 18 episode, Season 2 was a full-season 22.)

I hear the unusual order is believed to be a way for Fox to hedge its bet on the risky reboot. Changing a co-lead on a show could go either way. On today’s upfront call, Fox chairman Gary Newman gave NYPD Blue as an example of a show, which went through a lead replacement in Season 2 after star David Caruso exited and went to have a long and successful run with Jimmy Smits as a replacement. But there are also examples of a different outcome, including the recent female lead replacement on the CBS comedy Kevin Can Wait, which was rejected by viewers.

Everybody at Fox and Warner Bros. TV is hoping Lethal Weapon 2.0, starring Damon Wayans as Murtaugh and Scott as what is believed to be Riggs brother, will work. The short order is just an insurance policy for the network, which didn’t have much say in the matter.

“It wasn’t our choice,” Fox chairman Dana Walden said of the recasting on the Fox upfronts call this morning. “Our partners at Warner Bros. came to us and said that they could not deliver the show as it was.”

The license fee on Lethal Weapons is believed to have stayed the same though the budget covered by the studio is said to have gone up with the casting of Scott who had been sought after for series.