Your high school football coach lied to you. Football doesn’t build character. But it can sometimes show it. The fourth quarter of the Giants landmark 24–21 loss to the Tennessee Titans yesterday exposed Tom Coughlin’s Giants, and in the process jeopardized their season as well as, probably, Coughlin’s tenure with the team — I’ll give him until the end of the season. It also seriously derailed the once promising careers of Eli Manning and Plaxico Burress.

The most spectacular Giants collapse of the 21st century began with Manning getting off on the wrong foot. For some unfathomable reason, Manning cannot be coached out of the terrible habit of throwing the football while putting his weight on his back foot. In the fourth quarter, leading 21–0, Manning leaned back instead of stepping forward and floated a pass down the sidelines, over the head of Plaxico Burress, deep in Tennessee territory. Burress, who must think his job description doesn’t entail diving for difficult passes, stopped and let Titans D-back Adam “Pacman” Jones catch the ball. At least Burress was consistent. After watching Jones catch it, he stood and looked on while he ran it back upfield.

This might not have been significant if Frank Walker, up from his cornerback position, hadn’t decided to give Tennessee another huge boost, when, on the subsequent possession, he cheap-shotted Vince Young on a fourth-and-one which gaveYoung another chance at putting his team back in the ball game. Didn’t anyone on the Giants watch the Rose Bowl last year? You don’t give a man like this a second chance. The Giants gave him a second and a third chance.

With the Giants leading 21–14 and 2:44 left to play on fourth-and-10, rookie defensive end Mathias Kiwanuka sacked Vince young to end the game … except that Kiwanuka forgot to sack Young. Kiwanuka was having so much trouble dragging him down that he turned to the ref to see if he was about to draw a roughness call or to argue for a faster whistle. Whatever he was doing, Kiwanuka, who outweighs Young by almost 40 pounds, should have held on till someone in a striped shirt told him the play was over. His lack of focus was classic Coughlin Giants. It was the most baffling play I’ve seen all year. Young scrambled for 19 yards and a first down. Three plays later, Young threw to Brandon Jones for the tying touchdown, and there wasn’t a Giants fan anywhere who didn’t know that the game and the season were essentially over.

Individually and collectively, the Giants quit against the Titans. I wish there was a nicer way to say it, but there isn’t. And they didn’t quit when they were down, but, in the fashion of so many spectacular Giants fourth quarter debacles under Coughlin, they quit while they were ahead.

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The Giants and Jets are as different as two teams with the same record can be. The Jets don’t have nearly as much talent as the Giants — they probably don’t have as much talent as Houston, the team they beat yesterday 26–11. Outscored by 25 points this year and shut out twice, the Jets somehow, with a 6–5 record, have a shot at the playoffs. Is Eric Mangini doing it with mirrors?

Let’s look at what the Jets couldn’t do yesterday: They couldn’t run the ball against one of the worst defenses in the NFL. Leon Washington was the Jets’ leading rusher — and when was the last time you heard the term “leading rusher” used about a guy who gained 17 yards? Cedric Houston had one run for five yards and ten more that netted only eight. Kevan Barlow, too, failed to net as much as one yard per carry, with just five yards on eight tries. Specifically, that was five yards on one carry, zero yards on seven others. Much of this was because Texas had the best young linebacker in football in DeMeco Ryans who was in on 14 tackles, an amazing eight of them on the Jets’ side of the line of scrimmage. Mostly, though, the Jets couldn’t run the ball because they have a lousy running game.

There were, however, numerous things the Jets did right. They did a pretty good job of stopping the run themselves, allowing Texas just 25 yards (two fewer than the Jets gained), giving up just one sack on Chad Pennington (the Jets had four on Texans quarterback David Carr), and committing just one penalty for five yards (Houston had seven for 77). Those are the kind of positives that don’t instantly jump out at you when evaluating a team’s performance, but they’re a good illustration of how much better managed the Jets are under Mangini than they were under Herman Edwards.

The Jets also did one big thing very well yesterday. They stretched out the Texans’ secondary by throwing to their wide receivers, Laveranues Coles and Jerricho Cotchery – were there ever two football players whose names sounded more like characters in a B-western? — rather than the short dump-off passes which merely draw the defense closer to the line of scrimmage. Coles and Cotchery caught 16 of the Jets’ 24 completions for 221 of Pennington’s 286 yards passing. Moreover, they caught most of them early; midway through the third period they had accumulated fourteen catches between them, and the Jets, up 16-3, were ready to coast.

But that’s the difference between the Jets and the Giants: The Jets aren’t a great team, but they play all 60 minutes on the clock. In this case, they could have played it better if they had a running game. The lack of a running attack didn’t hurt the Jets this time, but it will the next time they face a team with a good passer and need to protect a lead late in the game by running the clock down.

For now, Jets fans can take some satisfaction in a defense that only a month ago was leading the league in yards allowed and had legitimate claim to being worst in the league. But over the last three weeks, they’ve given up just four touchdowns and 35 total points.

In fact, since being blasted by Jacksonville 41–0 on October 8, the Jets have allowed an average of only 16 points a game. They get a real break this coming Sunday, playing the Packers in Green Bay with a wounded Brett Favre and, if the surprisingly rosy weather predictions hold up, on a pre-Siberian winter field. If they win, they’ll take a 7–5 record into their last four games with an excellent chance at finishing 10–6.

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