Upset Watch: Week 15

Upset Watch appears every Thursday for ESPN Insider, as Football Outsiders uses a proprietary formula to forecast the expected point spread of each game based on current DVOA ratings ( explained here), along with home-field advantage and injury data. Each week, we highlight the most likely upset on a game with a line over three points, plus an additional game where a significant underdog has a strong chance to cover.

The big trend for Week 15 in the NFL seems to be superior teams favored on the road. Right now, seven different playoff contenders are favored on the road against teams that are essentially out of the playoff hunt. However, you can't write off the effects of home-field advantage, which is why these games make for a slew of possible upsets in Week 15. Here are the most likely upsets with a three-point spread or greater:

• Minnesota (+4.5) vs. Philadelphia
• Oakland (+4) vs. Kansas City
• Pittsburgh (+3) vs. Cincinnati
• St. Louis (+5.5) vs. New Orleans
• Tampa Bay (+5.5) vs. San Francisco

The game we're choosing for Upset Watch features a team coming off a big, emotional win, on the road to take on one of the league's most underrated squads. It also features two young quarterbacks trying to read two very strong secondaries so they can find the right targets in their two flawed receiver corps.

Upset Watch: Tampa Bay (+5.5) vs. San Francisco

The issue here is not that a trip to Tampa Bay qualifies as some sort of "letdown game" for San Francisco after its big home win against Seattle. Instead, the issue is that Tampa Bay is much better than most people realize. In fact, the Bucs have been better than their record all year long.

After eight games, the Bucs had the best DVOA rating of any 0-8 team in our database, going back to 1989. They ranked 23rd in the NFL, despite not having a win. Now, five weeks later, the Bucs have moved up to 13th in our ratings. The difference between the Bucs and the 49ers (who rank eighth) is about the size of what we usually consider home-field advantage, meaning this game is really a toss-up.

The improvement for the Bucs in their recent 4-1 streak has been entirely on defense. The offense ranked 21st in DVOA through Week 9 and ranks 24th for Weeks 10 through 14, actually dropping slightly. But the defense has improved from minus-3.7 percent DVOA through Week 9 (12th in the NFL) to minus-23.3 percent over the past five weeks (second, with only Seattle performing better).

A big reason for the improvement is that Darrelle Revis is healthier and is now being used in the role he played in New York: covering the other team's best receiver man-to-man. That's brought a dramatic improvement in Tampa Bay's defense against the opposition's top receiver, which in turn has improved the Bucs' pass defense overall. In Weeks 1 through 7, Tampa Bay allowed 9.5 yards per pass to the opponent's top receiver, with an 80 percent catch rate and 71 yards per game. Since Week 8, the first of two games where Revis took on Steve Smith one-on-one, Tampa Bay has allowed 6.5 yards per pass to the No. 1 receiver, with a 53 percent catch rate and 51 yards per game. (This includes the Week 12 game in which Revis was injured halfway through and rookie Johnthan Banks had to cover Calvin Johnson in the second half.)

So whom will Revis be covering? Although Michael Crabtree is finally healthy and last week played more snaps than Anquan Boldin for the first time this season, it's hard not to see Boldin as the 49ers' No. 1 threat. Does that mean Crabtree is in for a big game? Not necessarily.

A better Revis lets the Bucs use their safeties differently, and that helps Banks play better as well. He gives up more yardage, but only because quarterbacks throwing away from Revis are sending more targets his way. In Weeks 1 to 7, the Bucs allowed 44 yards per game to the opposing No. 2 receiver, with 9.8 yards per pass (including pass interference) and a 54 percent catch rate. Since Week 8, the total has gone up to 69 yards per game, and the catch rate is up to 61 percent, but the yards per pass has dropped to 8.3. The Bucs have also gone from six total interceptions in the first six games to 15 picks in the last seven.

The 49ers like to run a lot, of course, but the Bucs'  defense has been solid there as well. Not quite as good as last year, when it was the best run defense in the league, but good enough to rank seventh in run defense DVOA. And for all that they love running the ball, the 49ers have really struggled getting initial push at the line of scrimmage. They rank just 30th in our adjusted line yards stat, which measures offensive line blocking. It sets up to be a big game for Bucs linebacker Lavonte David, who leads the league with 18 run tackles that either lost yardage or prevented a third-down conversion.

For the Bucs' offense, the biggest weapon is the deep threat of Vincent Jackson rather than a chain-moving possession threat like Boldin. However, to win this game, Mike Glennon is going to have to figure out how to find his second and third reads and get the ball to guys like Tiquan Underwood and Chris Owusu, as well as tight end Timothy Wright. The 49ers rank second in the league defending the opposition's top receiver. This isn't because of any specific cornerback, as the 49ers tend to leave their cornerbacks on specific sides; instead, it's about the scheme and the strong rookie campaign of free safety Eric Reid.

The 49ers' defense ranks 24th against the pass on first down but fifth on second down and third on third down, so the space is open here for Glennon to make something happen with play-action early in series. The 49ers aren't particularly weak against play-action, but Glennon is strong there, with a 77.0 QBR using play-action as opposed to his 47.1 QBR overall.

One other thing Tampa Bay has to do to pull off this upset is show better discipline. The Bucs are this year's most penalized team, with 119 penalties (including declined/offsetting infractions) and a cool 1,000 penalty yards through Week 14.

Cover Watch: New York Jets (+11) at Carolina

In last week's Upset Watch, I noted that Carolina would need to switch up its strategy to upset New Orleans by passing on first downs and then running on later downs. It didn't happen, and the offense stagnated.

Well, this week Carolina is really going to have to switch up its offensive strategy, because the Jets have the best run defense in the league. DVOA says the Jets' run defense is 30.1 percent more efficient than average, which makes it one of the 10 best run defenses since 1989.

The Jets have a fabulous defensive line. Muhammad Wilkerson is a Pro Bowl-level player, Sheldon Richardson is a Defensive Rookie of the Year candidate and Damon Harrison is one of the best unknown players in the league. Unfortunately, the secondary has had huge problems this year, which makes the defense ridiculously unbalanced. The Jets are first in run defense -- and 20th in pass defense. If the Panthers want a dominant win instead of a close win, offensive coordinator Mike Shula is going to need to get creative and let Cam Newton win one with his arm.

Of course, while the Jets are the best run defense in the NFL, the Panthers are second. That means the Jets will be depending on Geno Smith to make very few mistakes if they want to win, and that's why this game is a much more likely cover than it is an outright upset.