Don’t blame this one on Peyton Manning. For years, his critics tried to pin a “choke” label on the best quarterback of the early 21st century, when the problem was actually the Indianapolis Colts’ defense. That was the problem again in the Colts’ 28–24 upset loss to the San Diego Chargers yesterday.

Manning had one of his best games ever, with 402 yards on 48 throws — that’s 8.4 yards per pass, 0.1 yards higher than Tom Brady averaged during New England’s unbeaten season, if you’re wondering — and had three TDs against two interceptions. But both the interceptions came off tipped balls. One of them, off the hands of running back Don Keith, should have given the Colts a 17–14 lead in the third quarter.

That was one of three scoring opportunities blown by the butterfingered Colts. Another momentum killer came in the first quarter, when wideout Marvin Harrison, who hadn’t caught a pass in three months after recovering from an injury, took in a 17-yard gainer from Manning at San Diego’s 22. He coughed up the ball after a hit from Chargers cornerback Antonio Cromartie.

Indianapolis’s biggest problem wasn’t its receiver, though, but its defensive coordinator. The Colts lost their much-hyped regular season match against the New England Patriots when they couldn’t hold a 10-point lead in the fourth quarter, and they couldn’t hold it because their defensive coordinator, Ron Meeks, called for a soft four-man rush, which Tom Brady picked to pieces. Just about any good quarterback, given time to throw, can pick any defense to pieces, and the Chargers’ Philip Rivers is a very good quarterback. Meeks turned him into a great quarterback by inexplicably pulling all of the Colts’ defenders downfield, giving Rivers the opportunity to counter with passes under the coverage, especially with simple screen passes. At the end of the third quarter, Rivers flipped a short screen to running back Darren Sproles — there wasn’t a Colts linebacker or defensive back within 10 yards of Sproles when he caught it, and he rambled 56 yards down the sideline for a touchdown that put the Chargers up 21–17.

San Diego caught the Indianapolis defense napping again on a vital fourth-quarter drive, when backup passer Billy Volek threw a short screen to rookie Legedu Naanee for 27 yards. (It could have been 42 yards, had a senseless 15-yard facemask penalty against Colts’ DB Marlin Jackson not been taken.) Two plays later, Volek ran a quarterback sneak for the winning TD. The book on how to attack inexperienced quarterbacks is to blitz them and keep them jittery and off balance; the aptly named Meeks ignored that chapter in the book and went to one with blank pages. In doing so, he turned the league’s best defense into something ordinary and gave the gutsy Chargers — who played most of the fourth quarter without Rivers at QB, and nearly the entire game without the league’s best runner, LaDainian Tomlinson — the confidence they needed.

Confident or not, San Diego won’t have a chance next week if Rivers, Tomlinson, and All-Pro tight end Antonio Gates (who was limping through the game with a dislocated toe) aren’t completely healed. With all three back and in good condition, the Chargers are, and have been for the last two months, the best team in the NFL.

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“I’m looking for my Academy Award on that play,” Brady said after the Patriots’ 31–20 victory over the Jacksonville Jaguars Saturday night. If I had a vote, I’d give it to him: His performance was certainly more convincing than anything I saw from Daniel Day-Lewis or Javier Bardem this year.

But then, Brady had better material to work with. The 2007 New England Patriots have reduced professional football to this: They protect their quarterback better than you protect yours — Brady was sacked just one time, on the Patriots’ first offensive play, and wasn’t even knocked down the rest of the game — and their quarterback picks you to pieces. Brady started the game by hitting on 16 consecutive passes, winding up 26 for 28. If you do that in the NFL, you win, no matter how you perform in the kicking or running game. It’s all passing and pass defense.

That doesn’t mean you don’t need a little finesse now and then. Six minutes into the third quarter, the gutsy Jags — the AFC’s thirdbest team this season, behind the Patriots and Colts, and thus the NFL’s third best team — were tied with New England at 14 all. This wasn’t where the Patriots had hoped to be at this point in the game, and there was some feeling that if they had to settle for a field goal on this possession, Jacksonville — with its great young quarterback, David Garrard — would seize the day. The Jags were certainly capable of it — Garrard actually ended up throwing for more yards than Brady, 278 to 262.

Then, as they’ve done in every pressure situation they’ve been in this season, the Patriots made the big play. Brady took the snap from center after faking as if the ball had gone directly to tailback Kevin Faulk, who swept to his left. Brady then jumped up and raised his right hand high, looking like the quarterback in that old Electro-Power football game. The ball, meanwhile, was on his hip, cradled by his left hand. He then effortlessly grabbed the ball with his right hand and flipped it over the middle to Wes Welker in the back of the end zone for the go-ahead touchdown — the Patriots, who were down 7–0 in the first quarter, never trailed again.

For all that, Jacksonville was still very much in the game right up until the end. Following Brady’s TD pass, Garrard engineered a 58-yard drive, which resulted in a field goal and made it 21–17 with four minutes left in the third quarter. Then, down by 11 with 4:34 left in the game, Garrard threw his only interception in New England territory. I would have been interested in seeing how the Patriots defended against Garrard in the final moments if the Jags could have cut New England’s lead to just four points — the Patriots’ defense, usually the biggest in the league in big game, had seemed tentative and uncertain all night.

The Jags’ defense, on the other hand, gave a textbook lesson in how not to defend against Brady. It stayed with a four-man rush throughout the game, even when it was obvious this set could not pressure Brady. Its linebackers played deep, and its safeties played deeper, which pretty much took Randy Moss (one catch for 14 yards) out of the game, but left Brady with single coverage on everyone else. (On most passing plays, Brady could have run out of the pocket and handed the ball to his receivers, and they still would have made their first down.)

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The Packers’ Brett Favre almost did hand the ball to one of his receivers with a wobbly underhanded pass to tight end Donald Lee just before halftime in Green Bay’s 42–20 rout of the Seattle Seahawks. The play, which came on third-and-eight, set up a touchdown run by running back Ryan Grant, whose two earlier fumbles had given the Seahawks two cheap first quarter TDs, after which the Seahawks and their coach, Mike Holmgren, demonstrated that they never should have been in the playoffs in the first place — by converting just five first downs in the second half. The press, as usual, focused on Favre’s three TD passes. But on this day, the Packers could have won just on defense (they held the Seahawks to only 199 yards on the snowy turf) and Grant’s running; he actually outgained Favre, 201 yards to 173. Both will have to do as well next week against the Giants if the Packers are going to go to their first Super Bowl since 1997.

Mr. Barra is the author of “The Last Coach: A Life of Paul ‘Bear’ Bryant.”