Some time before the end of the season — my guess is that it will be around Week 4, when the Arizona Cardinals come to the Meadowlands — the Jets and their fans are going to ask the question, “Wouldn’t we have been better off trying to get Kurt Warner?” Indeed, they would have. So would more than half of the teams in the NFL.

Warner is one of the best passers in pro football history and, even though it’s later in his career, one of the best in the game today. He’s better than Matt Hasselbeck or Jeff Garcia, and probably better than Donovan McNabb, or even Tom Brady — which is to say that given the same blockers and receivers, his career numbers would be better than theirs. That’s a pretty safe bet, since Warner has been playing with bad-to-mediocre talent for much of his career, and his numbers are still better than theirs.

In his first full NFL season (1999), he threw 41 touchdown passes and averaged 8.7 yards per pass attempt — one of the greatest seasons recorded by any NFL passer. (You’ll remember that everyone gasped at Brady’s 8.3 YPA average last year.) It’s mind-boggling to think what numbers Warner might have compiled if some NFL team had the brains to draft him out of the University of Northern Iowa in 1994.

As he starts the 2008 season, Warner is the third-highest-rated quarterback ever at 93.2, behind Steve Young and Peyton Manning, but you could watch him play all season without hearing anyone mention it. Brady, who has played behind the league’s best offensive line, is fourth at 92.9. It’s no stretch to imagine that if Warner and Brady switched teams, Warner would have at least three Super Bowl rings.

A Brett Favre comparison? Forget it. Favre is ninth on the all-time passer rating list at 85.7. Warner has led NFL passers in the most important passing stat, yards per attempt, three times. Favre has never led the league in YPA, even once. Warner, who is two years younger, makes about half of Favre’s yearly salary.

Warner’s mark of 9.9 YPA in 2000 is the highest since Norm Van Brocklin’s 10.1 in 1954. Neither Manning, Joe Montana, nor Dan Marino ever came within 0.7 of a yard of Warner’s 9.9.

It’s incredible to think that at age 37, after leading the St. Louis Rams to Super Bowls in the 1999 and 2001 seasons, Warner would be in a position to be called the most underrated quarterback in football. But there you are. Everyone remembers Warner’s story: cut by the Green Bay Packers in 1994, worked in a supermarket and collected food stamps to feed his family, finally made his NFL debut at age 27 after playing in the Arena Football League. What no one ever seems to understand is how good Warner is now. No one ever does.

In 2004, after leading the Giants to a 5-4 record, Warner was relieved of the starting QB job and the ball was handed to rookie Eli Manning. When he lost his job, Warner had a YPA of 7.4, with an interception of rate of 1.4%. Manning averaged 5.3 yards a throw the rest of the way with an interception rate of 4.6%, winning only one of their last seven games. Giants coach Tom Coughlin, not always the best judge of talent, later said he regretted not starting Eli Manning all season long, “so he’d have the experience.” Eli has had the experience of starting for the Giants ever since. Last season he averaged 6.3 yards a throw with 23 TDs against 20 interceptions; Warner, with the Arizona Cardinals, averaged 7.6 yards with 27 TDs and 17 Ints.

If NFL coaches were simply interested in winning, most of them would be hot to get Warner. Instead, they get caught up in “quarterback controversies.” The latest one involved Warner and the former USC Heisman Trophy winner, Matt Leinart. Earlier this year, Arizona coach Ken Whisenhunt announced that Leinart, despite two wretched, injury-plagued seasons, would be the Cardinal’s starting quarterback — presumably because, having paid so much money to get him, he felt pressured (as Tom Coughlin had with Eli Manning) to show some return on their investment.

Wisely, Whisenhunt changed his mind before opening day against the San Francisco. “I don’t know exactly how many interceptions [Warner] threw last year,” he told reporters, “but I knew he didn’t throw 27, and I knew he threw 27 touchdowns. So that’s something that’s kind of hard to ignore.” Unless, well, you coach football in the NFL.

Warner neatly carved up the 49ers in a 23-13 victory on Sunday, and next week, the Cards play a home game against the Miami Dolphins, followed by the Washington Redskins in D.C. There’s a very good chance that the Cardinals will be unbeaten when they play the Jets on September 28, and after that, for the second time in his career, Kurt Warner might stop being underrated.

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