Defensive tackle Tommy Kelly, signed Wednesday after being cut by New England, was in for 15 plays.
"He got a little push in the middle," Arians said. "It looked like getting off the boat he did pretty good."
Trips inside the 20-yard line were rare and neither team scored a touchdown, leaving the field goal kickers to fight it out. The Chargers did get to the Arizona 6 in the closing minutes, but third-string quarterback Brad Sorensen took a knee on three straight snaps.
San Diego's Nick Novak was good from 35, 39, 55 and 37 yards.
Arizona's Chandler Catanzaro kicked field goals of 42, 38 and 35 yards.
Leading 9-3, the Chargers went for it on fourth-and-goal from the 2 with 2 seconds left in the first half, but Kellen Clemens' pass to Dontrelle Inman was intercepted by Jimmy Legree, who returned it 68 yards before being dragged down on a horse-collar tackle by Inman.
That gave Arizona the ball at the San Diego 20 and Catanzaro kicked a 38-yarder to pull within three.
San Diego's Torrence Allen fumbled the second-half kickoff and Arizona's Jalen Parmale recovered, setting up Catanzaro's tying 35-yard field goal.
Chargers rookie Tevin Reese had a rough game with several drops. He also fumbled in the third quarter, but center Khalil Wilkes recovered and Novak kicked a go-ahead 37-yard field goal on the next play.
Arizona rookie quarterback Logan Thomas played the whole game. He completed 9 of 21 passes for 73 yards. He was intercepted by rookie Alden Darby from Arizona State in the closing minutes, giving the Chargers the ball on the Arizona 17.
"They played great defense and there were some things here and there that I could have done better personally, but I've just got to watch the tape and learn from it," Thomas said.
Thomas was "just very, very average," Arians said. "You can't take a sack at the 1-yard line. Either throw it away or get it to the check-down. It was a good learning experience for him."
Clemens, San Diego's backup quarterback, was 14 of 25 for 158 yards.
San Diego rookie Marion Grice, a sixth-round draft pick out of ASU competing for the fourth running spot, gained 79 yards on 17 carries. Branden Oliver, an undrafted rookie, had 71 yards on 16 carries.