1. Whisenhunt homecoming. Former Cardinals coach Ken Whisenhunt returned to University of Phoenix Stadium as the Chargers' offensive coordinator. His quarterback, Philip Rivers, averaged only 3.9 yards per attempt and threw one interception with no touchdown passes. However, the Chargers' first-team offense put together a 92-yard touchdown drive and generally outperformed the Cardinals' starting offense on this night. Both teams' running games were effective early. That provided some consolation for the Cardinals until the team lost running back Rashard Mendenhall (knee) and rookie first-round guard Jonathan Cooper (ankle) to injuries of unknown severity. Cooper rode a cart off the field and wasn't putting any weight on his left leg after the injury. Another player flew into his left leg from the side and behind, causing Cooper's left ankle to roll inside out. A serious injury to Cooper would undermine the team's efforts to upgrade the line. That seemed particularly true on this night, when the Chargers' Dwight Freeney dominated against Cardinals left tackle Levi Brown.
2. Williams at running back.Third-year running back Ryan Williams returned to practice late in the week and made his 2013 preseason debut late in the third quarter. Williams, troubled by knee issues lingering from a 2011 injury, gained 5 yards on his first play. He was the fourth running back to get carries in this game, after Mendenhall, Alfonso Smith and Stepfan Taylor. Rookie Andre Ellington was shaken up returning a kick right before Williams went into the game. Ellington then went back into the game on offense, replacing Williams. Williams returned when Ryan Lindley took over at quarterback in the final five minutes. He carried one more time and gained 5 yards. He ran well on his two carries. Time could be running out for Williams. Three other recent high draft choices for Arizona -- Cooper, tight end Rob Housler (ankle) and nose tackle Dan Williams (knee) -- left this game with injuries. Rookie seventh-round tight end D.C. Jefferson also left with an injury. This was a brutal night for Arizona.
3. Red-zone offense. The Cardinals wanted to focus on this area after settling for four field goals and a 12-7 victory in their most recent preseason game. They scored one touchdown in two red-zone possessions against San Diego. Housler dropped an accurate pass from Carson Palmer in the end zone, killing the first opportunity. Receiver Michael Floyd made an impressive leaping grab in the back of the end zone to score on the other red-zone possession. This was progress, in a way, but the shaky pass protection and injuries likely prevented Arizona from enjoying it.