EAST RUTHERFORD, N.J. (AP) -- Philip Rivers came back and not only beat the New York Giants in his first game against them since the draft-day deal in 2004, the quarterback might have stuck a dagger in their season.

Rivers capped a magnificent 80-yard drive with an 18-yard pass to Vincent Jackson with 21 seconds to play and the San Diego Chargers stunned the Giants 21-20 on Sunday for their third straight win.

"This hurts," tight end Kevin Boss said after New York (5-4) lost its fourth straight game. "It is a real painful loss. I thought we had it."

Rivers stole it for the Chargers (5-3) after the Giants settled for a late field goal after getting a first down at the San Diego 4 with 3:14 to play following a 33-yard interception return by Terrell Thomas. Instead of being up 10 points with roughly two minutes to go, New York was up six - and Rivers made them pay.

"We had a chance and you can't leave that team in the game," said Giants quarterback Eli Manning, the other major part in the 2004 trade between New York and San Diego. "You can't leave that team an opening. They are good and talented and if you have a chance to end it, you have to end it."

Rivers hit 6 of 8 passes in the game-winning march, finding Malcolm Floyd for 12 yards, connecting twice with Antonio Gates for 19 yards before combining with running back Darren Sproles on a 21-yarder that put the ball at the 18. On the next play, Rivers found Jackson behind cornerback Corey Webster in the right corner of the end zone for the win that has the Chargers well positioned for the second half of the season.

"It's a big emotional win," said Rivers, who threw for 209 yards and three touchdowns in his first head-to-head game against Manning. "I don't need a real reason why, but it ranks right up there with the win at Indy in the playoffs (2009). The link between me and Eli is always going to be there. So yeah, it's a little special. Any time you play against a team that won the Super Bowl, it's fun. It (the trade) didn't weigh into my mind and my thinking, but I bet it was there."

Chargers coach Norv Turner said Rivers seemed in complete control in the final two minutes.

"We struggled up front early, but we didn't over the last drive and that was big," Turner said. "We knew that we had enough time to get a touchdown and Philip has done that before. Our guys have great character and this was a character win."

Appropriately, the game ended with Shawne Merriman sacking Manning. San Diego drafted the linebacker in 2005 with one of the three draft picks the Chargers got from the Giants in the Manning deal.

"We showed a lot of team character to bounce back," Merriman said. "We never want to start off slow, but we've learned when we need to hit our stride."

Rivers also threw a 10-yard touchdown pass to Jackson in the second quarter and a 2-yarder to Kris Wilson in the third quarter that gave San Diego a 14-7 lead.

Manning, who was 25 of 33 for 215 yards, drove New York 60 yards on its next possession before settling for a 38-yard field goal by Lawrence Tynes that cut the lead to 14-10.

The Giants' defense, which gave up 112 points in the first three games of the losing streak, then helped them take the lead, recording three straight tackles for losses and forcing the Chargers to punt from their 4.

Domenik Hixon returned the ball to the San Diego 39 and Manning needed only six plays to put New York on top, hitting Kevin Boss with an 8-yard TD on a play when the Chargers were offside.

A bizarre play at the end of the Giants' opening drive cost them three points. New York lined up for a 39-yard field goal attempt, but Tynes never got the kick off. Jeff Feagles took the snap and Tynes said Feagles had both hands on the ball so he could not kick it.

"We are all very, very upset, very disappointed obviously in the loss," Giants coach Tom Coughlin said. "We played hard, did a lot of good things but obviously we didn't do enough."

Manning threw a 6-yard TD pass to Steve Smith for the Giants' other score.

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