"This is just free advice. Swallow your pride, pick up the phone and call Kap," Carter said on FS1's "First Things First."

"I believe he can make the difference on that football team."

The Jaguars -- and specifically Blake Bortles -- sucked this weekend. In fact, Bortles was benched in the 3rd quarter of Jacksonville's 20-7 loss to the Houston Texans.

Carter says the Jags had an opportunity to sign Kaepernick in the preseason but passed -- "it was strictly a political decision" -- but now, they need to pull Colin's phone number out of the trash.

"They made a mistake by not signing Kap," Carter said ... "They know it behind the scenes. [Co-host Nick Wright] and I know it. They talked to Kap but we know. It was strictly a political decision."

Carter explains, "He's a better thrower of the football than Blake Bortles. He's a better runner of the football. He's been a better winner. He's a better leader than Blake Bortles. So, you get what you pay for."

As we previously reported, Colin's been training every morning at 5 AM in the hopes he gets a call from an NFL team ... like the Jags.