The Patriots announced Saturday that Tebow was among their final cuts before the regular season begins, and Clarkson believes that could spell the end of Tebow's time in the NFL.
"It's time now to maybe just reconsider a different path to his ultimate dream. Tim might want to look to the CFL because he may have run out of options in the NFL,'' Clarkson told USA Today. "Sitting is not an option for Tim. He's ultra-competitive. He needs to stick to his strength, which is being in a competitive environment.
"Anyone who wants to work on their craft the way Tim does, he just needs to give himself a couple of days and really decide, 'Is this what I want to do?' Clearly, football is still in his blood.''
The Montreal Alouettes own the rights to Tebow in case the quarterback decides to make the move to the CFL to try to become Anthony Calvillo's backup and perhaps future successor.
However, the 26-year-old confirmed via Twitter on Saturday he doesn't want to quit on the NFL just yet.
"I will remain in relentless pursuit of continuing my lifelong dream of being an NFL quarterback," Tebow tweeted.
Too late, according to Clarkson.
"I haven't spoken to Tim in a while,'' he said. "My general thoughts now are, 'We're starting the NFL season. Right now, it's not realistic that he'd be a guy an NFL team is going to pick up.'"
Tebow completed 11 of 30 passes for 145 yards with two touchdowns and two interceptions in three preseason games with New England before being cut.