Almost four years after the Giants executed a blockbuster draft-day trade that made Eli Manning the centerpiece of their franchise, Manning played the signature game of his brief NFL career yesterday, looking cool in the Tampa heat and leading the Giants to a playoff victory over the Buccaneers.

The Giants’ 24–14 win was unexpected, and the way they did it was shocking: Manning played a virtually mistake-free game, while the Giants’ defense forced the usually unflappable Tampa Bay quarterback Jeff Garcia into a fumble, two interceptions, and several bad passes. With a great effort on both sides of the ball, it was the best game the Giants have played all year.

It would be tempting to say that Giants coach Tom Coughlin’s decision to fight hard for 60 minutes a week ago in the regular-season finale against the New England Patriots contrasts favorably with Buccaneers coach Jon Gruden’s decision to rest his top players late in the regular season. But early in the game, it was actually the Buccaneers who came out looking sharp and fiery and the Giants who looked rusty.

In the first quarter, the Buccaneers’ offensive line repeatedly overpowered the Giants’ defensive line, and a 10-play, 54-yard scoring drive gave Tampa Bay an early 7–0 lead. The Giants, meanwhile, had three punts and zero first downs in the first quarter.

That was largely because Tampa Bay defensive coordinator Monte Kiffin made stopping Giants running back Brandon Jacobs the centerpiece of his game plan. When Jacobs was in the backfield, the Buccaneers kept at least eight defenders close to the line of scrimmage, and when Jacobs got the ball, the Tampa Bay defense swarmed toward him. Jacobs ended the first quarter with four carries for negative-3 yards.

But once it became clear that Kiffin’s goal was to stop Jacobs, Giants offensive coordinator Kevin Gilbride won the in-game chess match with Kiffin and took advantage of the Bucs’ focus on Jacobs. Gilbride called bunches of short sideline passes to wide receivers Amani Toomer, Plaxico Burress, and Steve Smith, and he inserted Ahmad Bradshaw at running back as a change of pace from Jacobs. The result was 277 yards of total offense and the Giants’ first turnover-free game of the season.

Jacobs wasn’t completely shut down, though. He scored the Giants’ first touchdown on a screen pass when he ran to the line of scrimmage at the snap, as though he were going to block, but then turned around, caught a short toss from Manning, and ran five yards to the end zone. He scored the Giants’ second touchdown by barreling through the middle for eight yards, following an excellent lead block by fullback Madison Hedgecock. That gave the Giants a 14–7 lead they would never relinquish. The Giants extended that lead in the third quarter when Corey Webster recovered a Tampa Bay fumble on the opening kickoff of the second half, setting up a field goal that made the score 17–7. That was one of many outstanding plays for Webster, who started at cornerback in place of the injured Sam Madison. Webster’s assignment on defense was to cover the Buccaneers’ most dangerous weapon — wide receiver Joey Galloway — and he did it perfectly. Webster had an outstanding interception in the end zone to end the Buccaneers’ first possession of the second half: He stayed with Galloway as he ran 30 yards down the left sideline, maintaining inside position the whole way, and grabbed Garcia’s pass as if he, not Galloway, were the intended receiver. Galloway, who was bothered by a shoulder injury, caught one pass for 9 yards.

The other star of the Giants’ defense was Michael Strahan, who had a phenomenal game. On a second down in the second quarter, Strahan plowed through Buccaneers right tackle Jeremy Trueblood and sacked Garcia. On the next play, he caught Buccaneers running back Michael Pittman from behind on a screen pass, preventing what could have been a long gain and forcing Tampa Bay to punt. Strahan led the team with eight tackles.

The Giants began the fourth quarter with a 15-play, 92-yard drive that culminated with a 4-yard touchdown pass from Manning to Toomer. On that drive, Manning was accurate and poised, and the Giants’ offensive line manhandled the Buccaneers’ defensive line. Center Grey Ruegamer, starting in place of the injured Shaun O’Hara, was particularly effective and looked fresh while the Buccaneers wilted in the humidity and 79-degree heat.

That drive made the score 24–7, and although Tampa Bay did add a late touchdown and get the ball back with a chance at least to make things close, Giants cornerback R.W. McQuarters sealed the win with a fantastic interception in which he leaped in the air to catch Garcia’s pass and somehow managed to tap both feet down inbounds. The officials ruled him out on the field, but a replay review correctly changed the play to an interception, and that was the ballgame.

The Giants will now travel to Dallas and get their third shot at the Cowboys this season, after losing 45–35 at Dallas in week 1 and 31–20 at Giants Stadium in week 10. They’ll be bigger underdogs against the Cowboys than they were against the Buccaneers, and the Giants’ season may very well end in Dallas. But they’ll still be playing on the second weekend of January. That means this season, which began with low expectations for a lame-duck coach and a quarterback who hadn’t proven himself, has exceeded expectations.

Mr. Smith is a writer for FootballOutsiders.com.