Former Heisman Trophy-winning quarterback Tim Tebow of Florida won’t be on the Super Bowl field in Miami, Fla., on Sunday, but his expected prime-time, anti-abortion ad is keeping him in the spotlight and raising questions about the sometimes awkward balancing act between religion and sports.

"He has become sort of the epitome or exemplar of the engagement between Christianity and big-time sports,” said Tom Krattenmaker, author of the new book, "Onward Christian Athletes: Turning Ballparks Into Pulpits and Players Into Preachers.”

"I can’t recall ever seeing so much (attention) around one athlete: both incredible respect, incredible accomplishment on the field, sterling character off the field, combined with this level of controversy and discussion and hoopla.”

Religion and sports haven’t always been on the same team; just ask any pastor who’s found members of his flock out on the links on a Sunday morning instead of in the pews. At the same time, sport evangelism ministries are more than half a century old, and even St. Paul turned to sports metaphors in talking about running "with endurance the race that is set before us.”

Tebow’s public expressions of faith — from Bible verses painted on his face during games to the $2.5 million Super Bowl ad sponsored by Focus on the Family — have sparked a range of questions about what’s appropriate when God meets the gridiron.

Some observers say Tebow has every right to appear in a Super Bowl commercial, even though they might question whether it’s the best way to share his views.

"It could very well be a great message, but is it a good venue?” asked Paul Louis Metzger, who teaches theology and culture at Multnomah Biblical Seminary in Portland, Ore. "Is it helpful to the discussion, or does it up the volume, so to speak, on the culture war rhetoric?”

Some sports columnists have given Tebow a foul, saying the ad about a hot-button social issue is, well, out of bounds.

"Religion should not be part of sport. Period,” declared Chicago Sun-Times columnist Rick Telander in a recent commentary. The Religious Coalition for Reproductive Choice urged supporters to pressure CBS to pull the ad because they "object to the equation of being Christian and being anti-abortion.”

Though the contents of the ad haven’t been released, it’s widely expected to feature Tebow and his mother, who was advised to consider abortion when she was pregnant with Tebow because of a high-risk pregnancy.

"I know some people won’t agree with it,” Tebow has told reporters, "but I think they can at least respect that I stand up for what I believe.”