Coach Andy Reid revealed Thursday that Long's injury was to his knee and that the Chiefs are still evaluating the injury, but didn't think he suffered ligament damage.
"There's a chance he has to have surgery on it, but we'll see,'' Reid said.
Long was signed by the Chiefs in the offseason after he ended his retirement after one year. He wrote about the injury on his Twitter account Thursday.
"I did everything I could to get back for football," Long said. "Zero regrets. ... Focusing on controlling the things I can control. Yesterday was not one of those things!"
I did everything I could to prepare to get back for football. Zero regrets. I've been getting better everyday and having so much fun with my new team. Focusing on controlling the things I can control. Yesterday was not one of those things! Thanks for the well wishes.— Kyle (@Ky1eLong) June 10, 2021
Drafted 20th overall by the Chicago Bears in 2013, Long missed just one game over his first three seasons, in which he was selected to three consecutive Pro Bowls. He appeared in just 30 regular-season contests over his last four years with the team because of a variety of injuries. He announced his retirement in January of last year.