Colin Kaepernick’s chaotic workout Saturday has left a trail of controversy — and sources told Page Six that a host of behind-the-scenes issues include a letter Kaepernick wrote in fourth grade, legal arguments over a workout waiver, and even a pissed-off Jay-Z.

The controversial Kaepernick was meant to work out for NFL teams on Saturday in Atlanta, but minutes before the QB was to take the field at the Falcons’ training complex, his reps said they’d moved the session 60 miles away to a local high school. (Eight teams showed up, and Kaepernick appeared in a T-shirt that read “Kunta Kinte,” in reference to “Roots.”)

The stunned NFL then released a lengthy statement Saturday with a flurry of details, including a claim that Nike wanted to be at the workout to turn it into an ad. (The brand launched a Kaepernick commercial last year that garnered controversy, a sales boost and a Creative Arts Emmy.) Said the NFL on Saturday, “Last night, when Nike, with Colin’s approval, requested to shoot an ad featuring Colin and mentioning all the NFL teams present at the workout, we agreed to the request.” But Nike then said it did not have cameras at the workout, and just wanted permission to use the names of NFL teams. Read more in Page Six.