Seattle Seahawks cornerback Richard Sherman made headlines this week when he said he's "sure" free-agent quarterback Colin Kaepernick is being blackballed by NFL teams.

Cleveland Browns left tackle Joe Thomas offered a simpler explanation on Twitter Saturday morning for why Kaepernick has yet to sign:

My thoughts re: @Kaepernick7? Teams don't currently view him as a starting QB, and NFL teams accept ZERO distractions from their backup QBs. — Joe Thomas (@joethomas73) March 25, 2017

Thomas gets at the crux of the issue with Kaepernick: the reason he hasn't signed is likely a combination of the questions about his football ability and the concern that his social activism will be a distraction. How much of each side factors in to the equation is up for debate.

Though Kaepernick has only made positive headlines in recent weeks, including donating $50,000 each to Meals on Wheels and an initiative to deliver food and water to Somalia, there are rumors that NFL teams fear they will incite President Donald Trump to tweet negatively about them if they sign Kaepernick.

Even if that fear is unfounded, it could be just enough for teams to decide that someone who may be only a depth player isn't worth the trouble.

Several fans responded to Thomas by mentioning former Browns quarterback Johnny Manziel, who also remains unsigned. Thomas suggested this proves his point about teams not being willing to put up with any distractions from non-starters: