The 2021 NFL season has been one of the most unpredictable in recent memory, and yet another NFL titan fell in an unexpected spot in Week 15.

The Cardinals entered the week with a 10-3 record. They were traveling to Detroit to take on the Lions, who had a record of 1-11-1 and had just won their first game in Week 13.

It was a foregone conclusion that the Cardinals would beat the Lions. Arizona entered the week as 13-point favorites despite coming off a seven-point loss. The Lions may have a chance to cover that spread, but surely they wouldn’t give the Cardinals any trouble in a get-right game, right?

Not quite. Dan Campbell’s team was ready to play on Sunday and the Lions jumped out to a 3-0 lead after an 8:50 drive to start the game. They never relinquished that lead, dominating the Cardinals en route to a 30-12 victory.

The Lions hadn’t scored more than 30 points in a game since Week 1, and they had only scored 20-plus points twice before their victory over the Cardinals. That made their win all the more stunning.

But was it the biggest upset of the year? You could make a case for it, but there is still one notable game that outweighs it. Here are the five biggest upsets to date during the 2021 NFL season, starting with one of the biggest upsets in NFL history.

IYER: How Cardinals’ loss impacts NFC playoff race

Biggest NFL upsets of 2021

1. Jaguars over Bills (-16)

As impressive as the Lions’ upset of the Cardinals was, the Jaguars beating the Bills outright as 16-point home underdogs is a bit more impressive because of the numerous obstacles the Jaguars overcame in that contest.

The Jaguars logged just 218 total yards of offense in their 9-6 win over the Bills. They were without their top offensive player, James Robinson, and were still being coached by Urban Meyer, whose disastrous tenure in Jacksonville ended after just 13 games.

While the offense didn’t do too well, the Jaguars’ defense showed up in a big way and won the turnover battle 3-1 while sacking Josh Allen four times. That led them to their second win of the season, and last of Meyer’s NFL coaching career to date.

Considering that the Bills were favored by more points than were scored in the game, that’s pretty good for the Jaguars. The victory earned them a bit more respect — even if they haven’t won a game since then. After all, they are the biggest home dog to win a game outright in the last decade, per the Action Network.

2. Lions over Cardinals (-13)

Bettors who placed a Lions +13 ticket had nothing to worry about in Week 15. They demolished the Cardinals and looked like they should have been the 13-point favorites.

The Lions’ win over the Cardinals was truly a blowout. Detroit never trailed in the game and led by at least 14 points in the entire second half. The Lions were just the third team to hold the Cardinals to fewer than 23 points on the season, and one of those games came with Colt McCoy at quarterback.

Detroit didn’t just beat the Cardinals. They ran roughshod over them. Jared Goff had just his third, three-touchdown game of the 2021 NFL season. And above all else, the Lions befuddled the Cardinals’ offense. Arizona couldn’t move the ball consistently and struggled immensely in the red zone, where the Lions held them to just one touchdown in five red-zone appearances.

The Lions also made history, as they are just the third team since 1970 to beat a team with the NFL’s best record while having the league’s worst record.

You could make the case that, because of that stat, the Lions’ victory should be at No. 1 instead of the Jaguars. However, we still give Jacksonville the edge because their spread was larger and their coaching was much worse. But the Lions’ win is a clear-cut second.

MORE: Jaguars now have control of No. 1 pick in 2021 NFL Draft

3. Jets over Bengals (-11.5)

Remember when Mike White was going to be the Jets’ version of Tom Brady? That was a good time. That stemmed, largely, from White’s strong performance in his first NFL start against the Bengals.

White had to start against Cincinnati because Zach Wilson suffered a knee injury against the Patriots. He wasn’t given a chance by anyone, but he led the Jets to a surprising victory by throwing for 405 yards, three touchdowns and two interceptions. It was a close battle — the Jets won 34-31 — but that was more than two touchdowns better than they were expected to do.

White’s star lost its luster over the next few games and he was eventually replaced by Joe Flacco while Wilson was sidelined. Still, White led one of the most memorable upsets of 2021, and he deserves credit for carrying the Jets’ offense in that contest.

4. Broncos over Cowboys (-10.5)

The Broncos won this game 30-16 but it was much more dominant than that, really. Denver led 30-0 in the fourth quarter before allowing Dak Prescott and Co. to notch a couple of garbage-time touchdown drives.

The Broncos held the Cowboys to just 290 yards even with the garbage-time production included. It just goes to show that you shouldn’t bet against high-level defenses when they are big underdogs.

This game also played into the “don’t bet against Teddy Bridgewater” theory. He is 42-20 against the spread during his career, so covering a double-digit spread is usually easy for him. In this case, he managed to win outright while throwing for 249 yards and a touchdown. His defense did most of the work, but he did one crucial thing to help them out. He didn’t turn the ball over.

NFL PLAYOFF PICTURE: AFC, NFC Wild Card races after Week 15

5. Texans over Titans (-10)

There was talk about the Titans being the best team in the AFC when they faced the Texans in Week 11. After they lost 22-13 as double-digit underdogs, that talk largely dried up.

The irony is that the Titans mostly outplayed the Texans in this contest. They outgained Houston 420-190 and averaged 2.2 yards per play more than them. So, what went wrong? The Titans turned the ball over five times. That took away whatever edge that the Titans had personnel-wise, as they kept gifting the Texans good field position and taking away their own scoring opportunities.

This was a huge upset, but make no mistake. This game wasn’t about the performance of the Texans. It was all about the Titans’ struggles. This will stand out as a blemish on Tennessee’s resume, as the Texans have just three wins on the season. Their other two came against the Jaguars.