Observations from warmups before the Arizona Wildcats’ game against USC on Saturday night at Arizona Stadium (7:30 p.m., ESPN2):
* Arizona has changed its defensive lineup every week, and this week is no different. On the defensive line, it appears that PJ Johnson will start at defensive end. The Wildcats are down an end after Jalen Cochran suffered an arm injury last week at Oregon State. He isn’t dressed.
* The secondary also will have a different look. Scottie Young Jr. is listed as the starter at the Spur safety position. Jarrius Wallace will start at Bandit. Demetrius Flannigan-Fowles will start at free safety.
* At linebacker, backup “Will” Anthony Pandy is not dressed. WildcatAuthority.com reported that Pandy is suspended for this game. A UA spokesman declined comment. The good news: Jacob Colacion is dressed for the first time this season and will slide into No. 2 role behind Tony Fields II.
* Quarterback Khalil Tate has both ankles taped outside his shoes. That’s a new look for him. He’s been playing with a sore left ankle since Week 2.
* Free safety Isaiah Hayes participated in 7-on-7 drills. That's a good sign. He missed last week's game because of an apparent shoulder injury.
* Cornerback Jace Whittaker is dressed but did not take part in 7-on-7 or 11-on-11 work.
* Left tackle Layth Friekh appears to have a slight limp. He's going to start. He appeared in an Instagram photo earlier this week with a boot on his right foot.
Be sure to check Tucson.com and the Wildcaster app for updates during and after the game. You can also follow me on Twitter at @michaeljlev.
