Report: Some teams concerned about Colin Kaepernick's vegan diet

Why Colin Kaepernick remains a free agent has been a subject of great debate this NFL off-season, with every day seemingly bringing a new excuse for Kaepernick's unemployment.

Why Colin Kaepernick remains a free agent has been a subject of great debate this NFL off-season, with every day seemingly bringing a new excuse for Kaepernick's unemployment. 

The latest explanation, according to one report? He's a vegan. 

Kaepernick, of course, kneeled during the national anthem before games last season to protest racial injustice in America. The quarterback isn't the star he was when he led the 49ers to the Super Bowl a few years ago, but despite San Francisco finishing 2–14 last season, Kaepernick actually played OK and certainly seems at least worthy of a backup role. So what's going on?

NFL execs have repeatedly bashed Kaepernick's peaceful protest anonymously, so it seems likely that his protest is a big factor here. But teams continue to offer up alternative reasons for why Kaepernick isn't signed. The latest iteration in this genre, according to a report from NBC Sports Bay Area's Matt Maiocco, is Kaepernick's diet. 

At season’s end, Colin Kaepernick stated he was fully committed to football. But some teams are unconvinced and wonder about his vegan diet.

— Matt Maiocco (@MaioccoNBCS) March 31, 2017

• ROSENBERG: Why is Colin Kaepernick still looking for a job?

Makes sense. That must be why the Cardinals signed Tyrann Mathieu to a five-year extension last year just months after he announced he was going vegan. Recently retired NFL running back Arian Foster is vegan. Tom Brady, the greatest quarterback of all-time, is "almost" vegan.

Novak Djokovic and Venus Williams, two of the best tennis players of their generation, are vegan. (Djokovic eats "a little fish here and there.") Ultramarathoner Scott Jurek, who in 2015 ran 2,189 miles of the Appalachian Trail over a world record 46 days, eight hours and seven minutes, is also vegan. 

Vegans don't eat meat, so protein intake has to come from other sources, like grains, nuts and soy. But experts say that as long as athletes are getting enough protein in some form, there's nothing inherently wrong with a vegan diet. 

So again we ask: Why exactly is Colin Kaepernick unemployed?