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MIAMI -- Fans chanted Tim Tebow's name in derision. They hooted as he missed open receivers, got buried under blitzes and kept falling short on third down.

Then he led an improbable comeback that became the latest chapter in the legend of Tebow.

In his first start this year, Tebow rallied the Denver Broncos with two touchdown passes in the final 2:44 of the fourth quarter to force overtime, and Matt Prater's 52-yard field goal gave them an 18-15 win Sunday over the stunned Miami Dolphins.

"It's tough to say, but man, Timmy did a great job," said Dolphins center Mike Pouncey, who played with Tebow at Florida. "Hopefully the critics will get off him about what he can't do and talk about the things that he can do, and that's figure out a way to win the game, no matter what."

The Broncos appeared beaten when they trailed 15-0 with 5:23 left and took over at their 20. At that point Tebow was 4 for 14 for 40 yards, and Denver was 0 for 10 on third-down conversions.

"It was my fault we were in that position," Tebow said. "Silly things kept happening. On the sidelines, we were still believing. We wanted it, and they believed in me for more than 60 minutes."

In the frantic final minutes of the fourth quarter, Tebow led TD drives of 80 and 56 yards sandwiched around a successful onside kick. He scored a 2-point conversion standing up with 17 seconds left to tie the game.

In overtime, Denver's D.J. Williams sacked Matt Moore to force a fumble and recovered it at the Miami 36. Three plays later Prater hit the game-winner.

"It was never in doubt," coach John Fox jokingly said. His team became the first to rally from a deficit of at least 15 points in the final three minutes since at least 1983, according to STATS LLC.

The Broncos (2-4) won for the first time in the eight games they've played on the Dolphins' field. Miami (0-6) extended the NFL's longest losing streak to nine games, leaving the status of embattled coach Tony Sparano even more tenuous.

"Of course he's the head coach and he's going to take a lot of heat," receiver Brandon Marshall said. "But trust me, it's not him. Not just him. It's all of us."

The Dolphins lost for the 12th time in their past 13 home games.

"I'm just discouraged for the players in the locker room," Sparano said. "They work really hard, and we don't have anything to show for it right now."

Tebow started for the benched Kyle Orton, and for much of the game the Broncos sputtered. Tebow was sacked seven times as he struggled to identify blitzes, and several throws landed nowhere near a receiver.

As he walked to the sideline after one series stalled, spectators jeered, and Dolphins players gestured to the crowd for more noise.

"You can't lose confidence in yourself, or you've lost already," Tebow said. "When you get knocked down, you've got to keep getting back up."

That's what Tebow did. With the Broncos on the verge of being shut out for the first time since 1992, he led an eight-play touchdown drive that got them back in the game.

Matt Willis' 42-yard reception was a pivotal play, and Tebow threw a 5-yard scoring pass to Demaryius Thomas with 2:44 left to make the score 15-7.

Then came the onside kick. Miami receiver Marlon Moore leaped to catch the ball but bobbled it and the Broncos' Virgil Green recovered at their 44 with 2:31 left.

"They made the play. I didn't," Moore said. "It was just a bang-bang play. I had it, the dude turned the corner, hit me, it came out, they got it."

Tebow's strike to a diving Daniel Fells gained 28 yards to the 3. Two plays later, Tebow fooled the Dolphins by rolling left and throwing back to the right to Fells, who dived across the goal line for a 3-yard score.

Denver still needed a 2-point conversion to stay alive, and Tebow kept up the middle to score standing up. Prater missed field-goal attempts of 49 and 43 yards in regulation, but his kick with 7:24 left in overtime gave Denver the victory.

"I'm trying to search for answers," Miami running back Reggie Bush said. "I just keep coming back to embarrassing."

While the Broncos were two time zones from home, lots of fans wore Tebow jerseys, and the popular quarterback drew a big roar trotting onto the field for his first series. Tebow won a 2005 high school state championship and the 2008 national title with the Florida Gators in the same stadium.

Crowd loyalties were divided even at halftime, when the Dolphins paid tribute to the 2008 Gators. Seventeen former Gators and former coach Urban Meyer took part in the ceremony, drawing a mix of cheers and jeers.

Despite the salute to the Gators and Tebow mania, the stadium was almost half empty at the start -- a sign of growing fan discontent with the Dolphins.

The crowd was booing the home team before Miami's first series ended, but Denver move the ball no better. Together the two teams failed to convert their first 16 third-down situations.

Midway through the third period Denver had netted 2 yards on 10 pass plays, an average of 7 inches per play. But in the final 13 minutes Tebow went 9 for 13 for 121 yards, and he finished 13 for 27 for 161 yards. He ran for 65 yards in eight carries.

"He's a young guy, a good player," Fox said. "He's going to get better. We saw him get better today."

Game notes

Broncos RB Willis McGahee left the game in the third quarter with a broken hand. It was wrapped afterward, but he said he would be fine. Denver DE Robert Ayers sprained his knee, and DE Elvis Dumervil sprained his ankle. ... LeBron James tweeted: "Congrats to (at)TimTebow for that comeback win today. Impressive! He's just a winner." ... DE Jared Odrick registered the first sack of the season by a Dolphins lineman. ... Denver rookie Von Miller had his sixth sack of the season.