Hamburg winger Nicolai Muller will miss the next seven months after he ruptured a knee ligament in celebrating a goal.
Having scored eight minutes into Saturday's 1-0 home win over Augsburg, Muller performed a series of helicopter whirls before launching himself into a jump as he punched the air.
He landed awkwardly, and was clearly in pain as his team-mates ran to join in.
Hamburg coach Markus Gisdol said it was "certainly a downer, I have never experienced anything like it before".
Muller, 29, joined Hamburg from Mainz in 2014 and has twice played for Germany, most recently in 2013.
He ruptured the anterior cruciate ligament in his right knee, with his club confirming he is expected to be out for "approximately seven months".
Hamburg's sporting director Jens Todt said: "The diagnosis is a huge shock for us, a big blow for the start of the season and of course extremely bitter for Nicolai.
"We wish him a good recovery and will help him with that as well as we can."