Jared McCain's playful mood is in jeopardy on Thursday -- just hours after the 76ers star had a laugh with fans over his 2.5-pound bench press photoshoot, he tore a ligament in his thumb during team workouts.
Philadelphia announced the injury just minutes ago ... saying its shooting guard suffered a UCL tear in his right thumb and is "consulting with specialists on next steps and further updates will be provided as appropriate."

The timing is wild -- McCain, the 16th overall pick in the 2024 NBA Draft, was just having fun with fans who trolled him over recent team visuals.