BYU QB Riley Nelson out for season

BYU quarterback Riley Nelson is out for the season with a shoulder injury, putting an end to the unsuccessful quarterback rotation the Cougars have used in the first three games of the year.

Nelson injured his non-throwing shoulder against Florida State and an MRI showed a need for surgery, the school said in a statement Tuesday. BYU did not disclose the nature of the injury.

That leaves true freshman Jake Heaps as the starter for the Cougars.

"We will miss Riley's leadership, toughness and playmaking ability," BYU head coach Bronco Mendenhall said in the statement. "Unfortunately, injuries are part of football. Riley is a great young man and we will look forward to his return."

Nelson started all three games while sharing time with Heaps. He was held out the entire second half of a 34-10 loss to FSU after going 1 for 4 for 1 yard and an interception. He also had three carries for 8 yards.

On the season, Nelson completed 20-of-40 passes for 205 yards and two touchdowns while adding 148 yards and one touchdown on 31 rushing attempts. Mendenhall could not decide between his quarterbacks because they brought vastly different skills to the game. Nelson is more of a runner, while Heaps is a better pure passer.

"It's never fun to be injured," Nelson said. "I'm getting it taken care of as soon as possible so I can start my recovery and be back to help the team in the future."

The quarterback rotation has hit what is usually a very productive offense very hard. BYU ranks 100th in the nation in total offense, averaging 302.67 yards a game, and 101 in passing offense.

Perhaps even more telling, the Cougars have averaged just 4.65 yards per attempt -- worst in the country. Earlier in the day on the Mountain West Conference teleconference, before the Nelson news broke -- Mendenhall put part of the blame for that low number on his quarterback rotation. He also said his quarterbacks were holding on to the ball too long and the receivers were unable to get open as well.

The school that has produced the likes of Jim McMahon, Steve Young and Ty Detmer now stands at 1-2. Under Mendenhall, the Cougars have never finished ranked lower than 21 in total offense or lower than 17 in passing offense.

Andrea Adelson is a national college football blogger for ESPN.com.