Spain captain Álvaro Morata was taken to hospital after suffering a head injury during an AC Milan training session on Thursday, the team announced.
The former Atlético Madrid remained in the hospital on Thursday night under observation and is set to sit out Saturday's league game at Cagliari.
On Friday, Morata confirmed that he had been released, writing on Instagram: "Already home! A thousand thanks for your messages. Thanks to everyone that works in this marvelous club to always make us feel good."
In a statement made on Thursday, Milan confirmed the injury.
"Following a clash this morning in training Morata suffered serious cranial trauma," Milan said in a statement.
"He was rushed to hospital where an MRI scan returned negative results. Alvaro is feeling better and will remain under observation at the hospital to comply with the protocol for similar cases."
Morata, who started and scored in the Italian side's 3-1 Champions League win at Real Madrid on Tuesday, was hurt after an aerial collision with a teammate.
Spain coach Luis de la Fuente will announce his squad on Friday for the upcoming UEFA Nations League games at Denmark on Nov. 15 and against Switzerland three days later.