DENVER – People in New England and Kansas City perked up on Thursday night. Fans in Baltimore and Miami got a little more nervous.

The folks in Denver left Sports Authority Field feeling downright sick.

Thursday night wasn't supposed to go this way. San Diego was 10.5-point underdogs, already lost to Denver at home this year, and at 6-7 were on the verge of falling out of the playoff race. Denver was going to take a big step toward locking up the AFC's top seed with its eighth home win this season.

Everything is changed now after the Chargers' 27-20 upset win. The Broncos don't control the top seed in the AFC anymore. That would be New England, which can get the top seed by winning out because it already beat the Broncos this year and own the tiebreaker. And now the Broncos and Chiefs both have three losses in the AFC West race, although Denver owns that tiebreaker.

And suddenly the Chargers are 7-7, very much in the AFC playoff race, right behind 7-6 Miami and Baltimore for the sixth seed.

It wasn't supposed to go this way but the Broncos we've seen for most of the 2013 season disappeared after scoring an easy touchdown on the first drive. The team that was on pace to break the NFL's single-season record for points struggled mightily. Part of the problem was the Chargers kept the Broncos' offense off the field by sustaining drives against a defense that grows more suspect as the season goes on.

Denver was sloppy all night. There were two defensive penalties for 12 men on the field, which summed up its issues. And when the Broncos got a crucial stop with the Chargers pinned in their territory early in the third quarter, linebacker Nate Irving inexplicably jumped offside, and San Diego got a first down from the penalty. The Chargers took the gift first down and ate up 8:20 on that drive.

And near the end, with the Broncos trailing by just a touchdown, another longstanding problem for the Broncos bit them. Their porous offensive line allowed Corey Liuget to get pressure and hit Manning's arm on a pass. It went straight up in the air and linebacker Thomas Keiser picked it off with about five minutes left.

San Diego has suffered some harsh losses this year, so they needed to steal a game like Thursday night to stay in the playoff hunt. Ryan Mathews, a punch line for most of the offseason for his durability issues, ran hard all night, finishing with 127 rushing yards and a touchdown. Philip Rivers, who looked like he might be on the downside of his career after two bad seasons, was very efficient, as he has been all season. He threw two touchdowns to star rookie receiver Keenan Allen.

Now the Broncos have to win out and hope for help to win the AFC's top seed. Another loss opens the door for the Chiefs to steal the AFC West title.

A lot changed on Thursday night. For both teams.

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