OAKLAND --A fourth-quarter flurry led by Trevor Siemian, who took over for an injured Paxton Lynch, was not enough to prevent the Broncos from falling 21-14 to the Raiders at Oakland-Alameda County Coliseum on Sunday.

Siemian led the Broncos to back-to-back touchdown drives of 93 and 75 yards in the fourth quarter, nearly bringing the Broncos all the way back from a 21-0 deficit.

"I was proud of how our guys finished. We had two 70-plus [yard] touchdown [drives] to get us back in it in the fourth quarter," Head Coach Vance Joseph said. "Guys making plays, Trevor making plays with his legs and his arm."

However, it was not enough to prevent a defeat extended the Broncos' losing streak to seven, and it guaranteed that their franchise-record-tying streak of consecutive winning seasons will end at five, matching the mark set from 1983-87 and 2002-06.

Why did the Broncos fall Sunday?

1. BECAUSE AN EARLY TURNOVER GAVE OAKLAND MOMENTUM

It also squandered a prime opportunity to put the Broncos in front.

Denver took possession at the Oakland 24-yard line with 47 seconds left in the first quarter after a perfectly executed strip-sack fumble by outside linebacker Shaquil Barrett, and although instant replay reversed a 20-yard touchdown pass from Lynch to Devontae Booker into a 19-yard gain, the Broncos still had first-and-goal at the Oakland 1 with a chance to reach the end zone and take a 7-0 lead.

They never got there.

After Booker was stuffed on first-and-goal, Lynch rolled left on second-and-goal and lofted a pass to Virgil Green in heavy traffic in the end zone. But Raiders linebacker NaVorro Bowman arrived with the football and intercepted the pass.

"It was a play we had been working on all week," Lynch said. "Either I was going to run or throw it to Virg. After I faked it, I kept it. I probably had a chance to get around the edge, but I saw Virg flash open and I had the confidence in myself to make the throw, and I threw it to him, and it just got batted around to a couple of guys and it fell in [Bowman's] lap while he was laying on the ground.

"It was a freak play, but at the end of the day, I probably could have pushed it to the pylon and seen what could have happened after that."

The Broncos wouldn't run another play in Oakland territory until the fourth quarter, by which point they trailed 21-0. Oakland capitalized off the mistake, marching 80 yards in eight plays to take the lead for good on a 9-yard Derek Carr-to-Amari Cooper touchdown pass.

Lynch finished the game with 41 yards on 9-of-14 passing, but he was sacked four times for 23 yards in losses. He also scrambled twice for 20 yards. The Broncos mustered just three first downs on the nine drives Lynch led before being forced out of the game because of an ankle injury.

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2. BECAUSE CARR MADE PLAYS WHEN HE HAD TO**

The Raiders ran more often than they passed Sunday, but when Carr dropped back to throw, he was brutally efficient, posting a 136.5 rating on 18-of-24 passing for 253 yards.

His 26-yard pass to Marshawn Lynch on third-and-12 with 8:58 remaining after the Broncos brought a heavy pass rush didn't result in a score, but it allowed Oakland to drain another three minutes from the clock, reducing the Broncos' chances of a comeback after Siemian had led a 93-yard march to a touchdown that narrowed the deficit to 21-7.

With just over two minutes remaining, Carr dealt the knockout blow by finding Cordarrelle Patterson under an all-out rush on third-and-8. Patterson grabbed the pass and kept going for a 54-yard gain to the Denver 31-yard line. Oakland ran out the clock from there to doom the Broncos to another defeat.

3. BECAUSE THE OFFENSE COULDN'T STAY ON SCHEDULE

The Broncos couldn't get their offense moving on first or second down. Just once on their first 10 possessions did they manage to avoid a third down -- when Paxton Lynch ran 11 yards for a first down on a second-and-7 scramble.

The Broncos faced 10 third downs in the first three quarters of the game, converting two of them. Five of those 10 third downs required at least 10 yards to reach the line to gain, with the Broncos facing an average distance of 8.4 yards on those third-down attempts.