A third-round selection by the Rams in 2011, Pettis totaled 107 receptions and nine touchdowns in 47 games for St. Louis.
The Rams released Pettis last October after restructuring his contract earlier in the year. He finished with 12 catches for 118 yards and a touchdown in five games for St. Louis last season, and is now fighting for a roster spot with the Chargers at a crowded position.
Pettis, a Boise State product, worked mostly from the slot in St. Louis, with 75 of his 109 receptions coming as a slot receiver. But with Stevie Johnson and Keenan Allen working inside, Pettis has predominantly been used on the perimeter.
Listed as No. 2 on the depth chart behind Johnson at slot receiver, through two preseason games, Pettis leads the Chargers with five receptions for 39 yards.
"For me, I’m just trying to go out there and be as consistent as possible and gain the coaches' trust, and that’s just day in and day out," Pettis said. "That’s been my goal since I got here."
At 6-foot-3 and 203 pounds, the Southern California native has made some "wow" plays in practice, particularly in the red zone. Pettis, 27, also found a familiar face in San Diego with reserve quarterback Kellen Clemens, who played with Pettis in St. Louis.
"The chemistry is there," Pettis said. "I haven’t got as many reps in a game as I would probably like with him. But I’m just trying to work my way up the depth chart and get some more reps with him."
One of the draws to San Diego for Pettis was playing with an experienced quarterback like Philip Rivers.
"That was one of the things when I first came out here -- it was nice to see how Philip does his daily routine, just being a pro," Pettis said. "When you see all the success he’s had on Sunday, then just to come here and see him on the practice field and inside the meeting -- just the way his brain works and how smart he is -- it definitely makes it a lot easier for the receiver to know that he’s always on the same page as you."
Rivers said he’s noticed the work Pettis has put in.
"Austin’s done a nice job," Rivers said. "I haven’t been in there with him much, but I think what stands out to me from him is you can tell he’s played in this league, and made plays in this league.
"He shows up on the tape when you’re going back through the film on one-on-ones and things. He’s a guy that’s physical and really has picked up the offense well."
Along with the opportunity to play alongside Rivers, Pettis said he’s adapted nicely to San Diego’s scheme on offense.
"Personally as a receiver I love it," Pettis said. "There’s a lot of pass game, so you can’t go wrong with that. They’ve got a lot of great concepts in.
"Honestly, I think the best part about it is all of the routes. You really get to run every single route. Some teams may like in-cutting routes, out-cutting routes or a lot of speed-type routes. But really, they incorporate everything in this offense and I think that’s great, especially with the receiving core having so many diverse guys."