In postgame interviews, the young quarterback often starts by saying, “First, I’d like to thank my Lord and Savior Jesus Christ” and ends with “God bless.” He stresses that football is just a game and that God doesn’t care who wins or loses.

This combination of candid piety and improbable success on the field has made Mr. Tebow the most-discussed phenomenon of the National Football League season. Most expert analysts still consider him poor material for a pro quarterback. An inexperienced passer with awkward throwing mechanics and the build of a fullback, he likes to run over defensive players, which is a no-no in the NFL, whose starting quarterbacks are expensive and hard to come by.

But onward he and the Broncos have marched, winning six of their last seven games and now tied for the lead in their division as they face the Chicago Bears this Sunday. Mr. Tebow continues to defy his critics—and to embody the anxieties over religion that are dividing today’s sports world and embroiling players and fans alike.

Claims by athletes—”God helped me do that” or “I thank God that I was able to do that”—are so commonplace that they usually draw little notice. Most sports fans seem to think that such religious talk doesn’t really affect how the games are played or credit it with a powerful placebo effect. So what if Adrian Gonzalez of the Boston Red Sox has a Bible verse inscribed on his bat? Fine—whatever helps him to hit the long ball.

But Mr. Tebow has never been content to leave his evangelical faith on the field. Well before he became the starting quarterback for Denver, he was a lightning rod in America’s intermittent culture war of believers vs. secularists.

In 2010, while still at the University of Florida (where he won the Heisman Trophy and helped the Gators to win two national championships), Mr. Tebow filmed a Super Bowl commercial for Focus on the Family, the mega-ministry known for its conservative political advocacy. The ad is about how Mr. Tebow’s mother was advised to abort her son following a placental abruption, but she refused and, well, now we have Tim Tebow.

Mr. Tebow may or may not enjoy long-term success as an NFL quarterback. His current streak will run its course, and the Broncos might well move on to another quarterback, one who is more obviously suited to the pro game.

But win or lose, Tim Tebow will compete hard—and when he’s done, he will thank God and remind all of us that it’s just a game.

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