West Ham say striker Michail Antonio is in a stable condition and "conscious and communicating" after a road accident.
In a statement, West Ham said Antonio is "currently under close supervision at a central London hospital".
The club added: "At this difficult time, we kindly ask everyone to respect the privacy of Michail and his family.
"The club will make no further comment this evening, but will issue a further update in due course."
The club said Antonio's road accident happed on Saturday afternoon in the Essex area.
West Ham face Wolves in their next match in the Premier League on Monday (20:00 GMT).
Antonio, 34, joined West Ham from Nottingham Forest in 2015 and has since scored 68 goals in 268 league appearances for the club.
Several clubs including Premier League sides Arsenal, Chelsea and Manchester City replied to an earlier statement from West Ham on X, external sending their best wishes to Antonio.
The Premier League also replied, adding the "thoughts and prayers" of everyone at the organisation are with "Antonio, his family, friends and all at West Ham".
Antonio is West Ham's all-time record Premier League scorer.
He has scored one goal in 15 appearances for the Hammers this season, finding the net in a 4-1 victory at home to Ipswich at the start of October.
The former Reading and Sheffield Wednesday striker was a key member of David Moyes' Europa Conference League-winning side, starting the 2-1 victory over Fiorentina in the 2023 final.
The Jamaica striker has five goals in 21 appearances for his country.
Antonio began his footballing journey with non-league Tooting & Mitcham before moving into the professional ranks with Reading.
He has also had spells with Cheltenham, Southampton and Colchester.