Everton winger Aaron Lennon was detained under the Mental Health Act by police over concerns for his welfare.
The 30-year-old was taken to hospital “for assessment” after police were called to Salford on Sunday.
Lennon is now “receiving care and treatment for a stress-related illness”, his club has said.
The England international, who joined Everton from Tottenham in 2015, has not played for the first team since February.
Greater Manchester Police said: “Police were called at around 4.35pm to reports of a concern for the welfare of a man on Eccles Old Road.
“Officers attended and a 30-year-old man was detained under section 136 of the Mental Health Act and was taken to hospital for assessment.”
News of Lennon’s admission has led to an outpouring of support on social media from those involved in the game, as well as fans of his current and former clubs.
Everton tweeted on Wednesday: “Thank you for all the kind messages for Aaron. We are supporting him through this and his family has appealed for privacy at this time.”
Lennon’s representative, Base Soccer Agency, tweeted: “Everyone at Base Soccer sends their support to @AaronLennon12 – get well soon and stay strong.”