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DENVER -- Once again, the crowd chanted "Tebow! Tebow!" as the Denver Broncos trudged off the field in defeat Sunday.

Only this time, the fans were imploring coach John Fox to keep Tim Tebow under center after the Broncos lost to San Diego 29-24 despite Tebow's best efforts to rally Denver from a 16-point fourth-quarter deficit.

Tebow ran for a touchdown and threw for another after replacing Kyle Orton to start the third quarter and had one final shot for the win before his pass fell incomplete in the end zone on the final play.

"Tim Tebow sparked the team today. (But) we haven't had a chance to watch the tape, we haven't had a chance to watch the film, we haven't had a chance to visit as a staff," Fox said. "So, I think at this point -- we have a bye week -- we do need to improve offensively, and it will all be up for discussion."

Neither quarterback had any indication who would line up in two weeks when the Broncos (1-4) visit the Miami Dolphins, whom the Broncos tried to trade Orton to in the summer before talks broke down and he became Denver's starter.

"I have no idea," Tebow said. "Thankfully, I don't have to make those decisions. Other people do that and I just go play football."

"It's his decision," Orton said of his coach.

And Fox indicated he would take his time making up his mind.

"I don't put time limits on things," he said. "We will evaluate it and make the best decision for the team."

While all the drama was surrounding Tebow, Philip Rivers overcame two big turnovers, a banged-up backfield and a tough time in the red zone to guide the AFC West leaders to another hard-fought victory in what he calls his favorite road venue.

"I didn't have much time to watch it," Rivers said of Tebow's inspiring play. "I was more worried about us getting to 4-1."

Nick Novak kicked five field goals and Ryan Mathews ran for a career-best 125 yards despite a strained right calf.

After a slow start, Tebow found a rhythm that threw off the Chargers.

"It changes (the tempo) because he's a fresh body," cornerback Antoine Cason said. "He has a lot of energy. He goes out there and plays with energy, the crowd got behind him a little bit. They went out there and did some things that got them back into the game."

Fox decided to shake things up after Orton completed 6 of 13 passes for 34 yards with no touchdowns and an interception in the first half.

A fan favorite, Tebow was cheered the instant he trotted onto the field for Denver's first possession in the third quarter. The crowd was so loud that Tebow couldn't hear the play call in his helmet.

Tebow was rusty after having played just a handful of snaps this season and not throwing a single pass before Sunday, bobbling his second snap and throwing his first pass at Eric Decker's shoe tops for no gain.

The Broncos punted on their first three possessions under Tebow before the former Florida star scored on a 12-yard run as Orton clapped from the sideline. McGahee's 2-point conversion cut San Diego's lead to 26-18 with 6½ minutes left.

"He came and gave us a spark," McGahee said. "That's Tim Tebow. Everybody has been cheering for him for the longest. Now he finally got in and moved the ball for us."

Robert Ayers sacked and stripped Rivers on the ensuing possession, and cornerback Andre' Goodman recovered at the San Diego 41 with 4:38 left.

Knowshon Moreno turned a short screen pass from Tebow into a 28-yard touchdown. But after a time out, Pro Bowl receiver Brandon Lloyd couldn't come down with the 2-point conversion pass, which was stripped away by Cason as they tumbled out of bounds.

Rivers hit a third-down pass and linebacker D.J. Williams was whistled for a personal foul in the closing minutes, and Novak's fifth field goal, this one from 35 yards, made it 29-24 with 24 seconds remaining.

Tebow hit Lloyd for 20 yards and tight end Daniel Fells for 31, though. He raced downfield and spiked the ball at the Chargers 29 with a second left.

Tebow took the snap, scrambled around for more than 10 seconds and then threw into the end zone. The ball fell incomplete -- just like the last time these teams met, on Jan. 2, when a bunch of Chargers preserved a 33-28 win by batting down his desperation heave into the end zone.

Tebow completed four of his 10 passes for 79 yards. He also ran six times for 38 yards.

"It's such a dramatic change when the quarterback changes," Chargers coach Norv Turner said. "It's really a whole different offense for our guys to handle."

Cassius Vaughn returned an interception 55 yards for Denver's first defensive TD in five seasons, but he was beaten badly by Malcom Floyd on a 43-yard touchdown with 13 seconds left in the first half that put the Chargers ahead 23-10.

That score came after the Broncos burned just 45 seconds off the clock on what turned out to be Orton's final series.

The question now is whether it was just his last chance of the day or if it signaled an end to his time in Denver, where he's 6-21 over his last 27 starts.

Game notes

Broncos rookie LB Von Miller was replaced in the base defense by Mario Haggan after the first two defensive series but still managed to a sack in his fourth consecutive game. ... Chargers RB Mike Tolbert left the game with a concussion after gaining 49 yards on five carries and three catches. ... Broncos S Brian Dawkins (neck) didn't play the second half.