The Chargers (8-7), who have won three straight games for the first time this season, need more help to end a three-year playoff drought. They have to beat Kansas City at home next Sunday and have Miami and Baltimore both lose.
Oakland (4-11) helped San Diego, too, by committing a dozen penalties. Mike Jenkins was penalized 15 yards for taunting Ryan Mathews after he pushed the running back out of bounds. Allen scored six plays later.
The game was tied at 10 after a sloppy first half that included three turnovers by the Chargers and seven penalties for 39 yards by the Raiders.
The only score of the first half that wasn't set up by a turnover was a 27-yard field goal by Novak with 2:42 left in the first quarter.
Early in the second quarter, Rivers wasn't ready for a shotgun snap and the ball bounced off him for a fumble that was recovered by former San Diego State linebacker Miles Burris at the Raiders 42.
The drive stayed alive when Mychal Rivera leaped to catch a 37-yard pass from Matt McGloin, and Darren McFadden scored on a 5-yard run on the next play for a 7-3 Oakland lead.
Rivers was picked off by Mike Jenkins to end San Diego's next drive, but Eric Weddle then intercepted McGloin at the Raiders 20, deflecting the ball to himself. That set up Ryan Mathews' 7-yard run and the Chargers regained the lead at 10-7.
San Diego forced the Raiders to punt from their 40 but rookie Keenan Allen's fumble was recovered by Shelton Johnson at the 16. The Raiders had to settle for Sebastian Janikowski's tying 20-yard field goal with 10 seconds left before halftime.
Novak kicked three more field goals in the second half, from 48, 28 and 33 yards. Janikowski added a 42-yarder.
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