Colin Kaepernick Looks Solid In New Workout Video ... W/ CeeDee Lamb, Jaylen Waddle

Colin Kaepernick hasn't played a down of football since 2017, but he's not showing any signs of rust ... 'cause the quarterback looked as good as ever in a recent workout with a bunch of NFL superstars.

The 35-year-old free agent just posted highlights from his training sesh at Nike headquarters ... and the guys in attendance made it look like the Pro Bowl.

While players like Jaylen Waddle, CeeDee Lamb, Najee Harris and Jaxon Smith-Njigba showed up, Kap was clearly the star of the show ... putting his arm on display as he hit his targets.

"Man, he looks great," Patriots receiver Kendrick Bourne said of the workout. "He looks good, the arm looks strong. He got a rocket of an arm ... he got…