The Raiders led by 21 points going into the final quarter but saw that advantage cut to just seven before long, as the Chargers scored two touchdowns without reply.
However, Pryor came up with a big play late on when he turned a potential sack into a third-and-long conversion to set up a field goal attempt that saw the Raiders move more than a score clear of San Diego.
"That's what the kid brings to us. Terrelle brings that ability when things aren't right, when things break down, he brings that ability to make plays," Allen told The AP.
"He's made a habit out of doing that his whole career: a defensive score, an interception to seal the game. That's what we expect out of him. He's been a playmaker for us and he'll continue to be a playmaker for us," Allen added.
The result leaves both teams with a 2-3 record after five games this season.