This is the most anticipated game of the weekend, matching a record-setting quarterback who calls his own plays against his arch-nemesis, a cerebral coach whose voter registration probably reads “Genius William Belichick.” But do not ignore the Patriots’ offense and the Colts’ defense, two underrated units that also get a say in deciding which team emerges triumphant.

WHEN INDIANAPOLIS HAS THE BALL

Many football observers have assumed that injuries in New England’s secondary will give Peyton Manning the chance to finally overcome his dismal history against New England. But Manning’s past performance against the Patriots is not that bad. True, he was horrid in last year’s AFC Championship Game, but the MVP has thrown for 250 yards in each of the teams’ last two regular season meetings, only to have last-minute drives ruined by a stuffed Edgerrin James plunge on fourth-and-goal and a miss by kicker Mike Vanderjagt.

Manning’s success comes in part from his ability to read defenses and adjust the offense at the line of scrimmage. With so many weapons and his renowned ability to sell the play fake, Manning can take advantage of any hole the defense gives him.

But the Patriots reduce Manning’s effectiveness from otherworldly to merely above average by confusing him with shifting defensive schemes, often pressuring him with four or even three pass rushers. It’s also worth noting that Manning was sacked nine times in six games against 3-4 defenses this year, but only four times in nine games against 4-3 defenses. That’s why the most important injured Patriot is not cornerback Ty Law but Pro Bowl defensive lineman Richard Seymour, listed as questionable.

Colts right tackle Ryan Diem, whose mistake allowed Denver’s Reggie Hayward to sack Manning last Sunday, is the weakest link in Indianapolis’s pass protection. He’ll have to face linebacker Willie McGinest, who has a history of huge plays against the Colts: Last year he kept James from the game-winning score in the final seconds and this year his sack of Manning led to Vanderjagt’s long-range miss.

What about those injuries in the secondary? With both starting cornerbacks out for the year, New England is starting undrafted rookie free agent Randall Gay alongside their former nickel back, Asante Samuel. Wide receiver Troy Brown has become the nickel back, and on dime situations linebacker Don Davis comes in as a safety.

Despite redefining the word “patchwork,” the Patriots actually had the best defense in the league against no. 1 receivers, including 11 interceptions. But they had one of the worst defenses in the league against no. 2 receivers, allowing big games to guys like Antonio Bryant, Johnnie Morton, and Marty Booker. And when injuries turned nickel backs into starters, the Patriots began to give up huge games to third receivers as well. Brandon Stokley could have a game akin to the one Ricky Proehl enjoyed against the Patriots in last year’s Super Bowl.

WHEN NEW ENGLAND HAS THE BALL

Indianapolis boasts by far the best offense in the NFL, but the addition of Corey Dillon and continued growth of Tom Brady this season transformed the New England offense into a top five unit as well. According to Football Outsiders’ Running Back Success Rate metric, only Curtis Martin was a more valuable running back than Dillon this season. Dillon’s hidden talent for picking up the blitz will be an important part of neutralizing the strength of the Colts defense – the pass rush.

The Colts were tied for second in the league in sacks, but the Patriots were fifth in fewest sacks allowed. An injury to Colts pass-rush specialist Robert Mathis means the Patriots can pretty much control the pressure by doubling NFL sack leader Dwight Freeney with Dillon or tight end Daniel Graham. The downside of this strategy is that the weakness of the Colts pass defense comes against running backs and tight ends, and you can’t catch a pass when you’re busy blocking.

While Brady likes to spread the ball around with multiple receivers, the cold weather and need to control the clock will mean a lot of carries for Dillon. And although the Colts’ pass defense improved over the course of the season, their rush defense declined.

But the Colts’ run defense does come into the game with one strength, and it directly counters a favored Belichick strategy. The Patriots go for it on fourth down more often than most other teams, while the Colts were fourth in the league in preventing conversions in power situations: runs on third or fourth down with 2 or fewer yards to go. The league average is 67% success; the Patriots had 76% success, but Colts opponents had only 54% success.

The Patriots have averaged 30 points in the last three games between these teams, and their balanced attack will keep the game close even if Manning is having a good day.

SPECIAL TEAMS

In a close game, this is a big advantage for New England. Adam Vinatieri is considered the NFL’s pre-eminent cold weather kicker. He also led the NFL this year in field-goal percentage and didn’t miss a single kick under 47 yards. The talkative Vanderjagt struggled through an off-year, missing five field goals and even an extra point.

Indianapolis does have an advantage when they have to punt, as Hunter Smith was second in the NFL in gross punting average and the Patriots return punts poorly.

OUTLOOK

Not since Charlton Heston has anyone had this many monkeys riding his back. Manning has to prove he can beat the Patriots, that he can win in the cold, and that he can win big games in the playoffs. The injuries to the New England defense make this the best opportunity he may ever get to prove all three, but an improved Patriots’ offense will score plenty of points as well.

This game will resemble the two regular season games more than last year’s AFC Championship: not a rout, but a close game fought until the final seconds.

Pick: Colts – unless Seymour plays.

Mr. Schatz is the editor in chief of Football Outsiders. Michael David Smith provided extra research for these articles. For more state-of-the-art football content, please visit www.footballoutsiders.com.