GLENDALE, Ariz. -- Ryan Mathews is off and running this preseason, and Jonathan Cooper's season could be over before it really began.
Mathews, slowed by two broken collarbones a year ago, carried 14 times for 57 yards and a touchdown, and the Chargers beat the mistake-prone Cardinals 24-7 for their first preseason victory under new coach Mike McCoy. Mathews did fumble the ball at the Arizona goal line, but even that play turned in to a San Diego touchdown.
The Cardinals lost several players due to injury, including left guard Jonathan Cooper, the team's first-round pick who broke his left leg and was helped off the field in the third quarter.
"We don't know if it'll be the season, or if he'll get to return," Cardinals coach Bruce Arians said, "Right now it's looking like the season."
Arizona's Rashard Mendenhall carried six times for 47 yards before leaving with an ankle injury.
The Chargers blocked a punt, blocked a field goal and returned a fumble for a touchdown -- all in the first half.
"We talk about being a smart football team," Arians said, "and that's probably the dumbest 30 minutes of football that I've ever seen."
Philip Rivers completed 10 of 18 passes for 71 yards with an interception. Arizona's Carson Palmer was 12 of 23 for 122 yards and a TD.
"This is the way we like to play week in and week out, with all three phases making plays and doing their job to the b est of their ability," McCoy said.
Arizona's problems began at the end of its first possession when Darrell Stuckey blocked Dave Zastudil's punt and the Chargers recovered at the Arizona 34. But a false start penalty pushed San Diego back, and Nick Novak's 51-yard field goal try was no good.
After a Cardinals three-and-out, San Diego went 92 yards in 12 plays, using up 6:51 of the first quarter. Mathews dived over the middle into the end zone, the first points allowed by Arizona's first-team defense in the preseason. The drive featured an unnecessary roughness penalty against the Cardinals' Ronald Talley.
Early in the second quarter, Arizona rookie Tyrann Mathieu hit Rivers' arm as he threw and the ball popped into the air. Jasper Brinkley intercepted and lateraled to Patrick Peterson, giving the Cardinals the ball at their 47. The Cardinals drove to the Chargers' 8-yard line, but on third-and-goal, Rob Housler dropped Palmer's pass in the end zone. Then Kwame Geathers blocked Dan Carpenter's 26-yard field goal try.
The wild second touchdown came a short time later.
The third pass interference penalty of the game against Arizona cornerback Jerraud Powers put the ball at the Cardinals' 1. Mathews went over the middle, but the ball popped free. Cardinals safety Rashad Johnson picked it up but, in an ill-advised move, lateraled to Sam Acho.
Acho was hit by Antonio Gates and again the ball popped in the air. Another San Diego tight end, John Phillips, grabbed it and returned it 3 yards for the score to make it 14-0.
"It's not the conventional way to score," Rivers said. "I don't know if I've seen a play like that in a long time."
A challenge by McCoy backfired and set up Arizona's touchdown.
Palmer threw over the middle to Andre Roberts, who dropped the ball. But McCoy challenged that it was a fumble, and indeed it was. However, officials ruled that Roberts, not the Chargers, recovered at the San Diego 16. On the next play, Palmer threw to Michael Floyd for the only touchdown for Arizona's first-team offense in the preseason.
The Chargers also scored on Fozzy Whittaker's 5-yard run and Novak's 50-yard field goal.
Cooper, the seventh pick overall out of North Carolina, had been a starter virtually since he arrived in Arizona.
"You just feel sorry for him, being a rookie and this only being his third preseason game," teammate Larry Fitzgerald said. "He's a big part of who we're going to be and our identity moving forward, not only for this year but for years to come. You feel really bad for him."
Ken Whisenhunt, fired as Arizona head coach after last season, returned to University of Phoenix Stadium as the Chargers' offensive coordinator.