EAST RUTHERFORD, N.J. — Five years after being traded away in a draft-day swap for Eli Manning, Philip Rivers came back and stuck it to the New York Giants.

Rivers capped an 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, posting their third straight win while handing New York its fourth straight loss.

San Diego (5-3) is now well positioned for the second half of the season. The Giants (5-4) can only shake their heads in disbelief after blowing their first 5-0 start since 1990.

"It's a big emotional win," said Rivers, who threw for 209 yards and three touchdowns. "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."

Rivers had the Giants to thank for giving him the chance to pull the game out.

Giants cornerback Terrell Thomas returned an interception 33 yards to the Chargers 4 with 3:14 to play. If Manning and company had punched the ball in, the game would have been over.

But a first-down holding penalty on Chris Snee pushed New York back 10 yards and it settled for Lawrence Tynes' second field goal, a 22-yarder with 2:07 to play for a 6-point lead."We had a chance and you can't leave that team in the game," said Manning, who was 25 of 33 for 215 yards and two touchdowns. "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 did. He hit 6 of 8 passes in the game-winning march, hitting Malcolm Floyd for 12 yards, two to Antonio Gates and a 21-yarder to Darren Sproles that put the ball at the 18. On the next play, Rivers found Jackson in the right corner of the end zone for the game-winner.

"Vincent just came open and separated himself from the defender," Rivers said. "On that play, he was probably the last option to get the ball by the way it set up. But we had all that field and I just wanted to give him a chance to get to it."

Jackson also caught a 10-yard TD pass in the second quarter.

"He's calm and confident and that just rubs off on everyone else," Jackson said of Rivers. "It didn't matter what the score was or how much time was left. We were going to get the job done."

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