BOISE, Idaho (AP) - Chris Petersen and his staff are back at work this week with one big goal in mind: Filling key holes in a Boise State defense that was among the nation's best last season.

The list of open spots is extensive. The Broncos are looking for two starting cornerbacks and a nickelback in the secondary. Up front, Petersen is looking for a pair of young or inexperienced players to emerge at linebacker and another on the line.

The first chance to make a good impression started Monday - the first of 14 practices.

Petersen said Monday he's excited to see players compete on a defense that lost six starters.

Petersen also said he's impressed with the improvement of senior quarterback Joe Southwick, who led the Broncos to a 11-2 record last year.