West Ham say striker Michail Antonio is in a stable condition and "conscious and communicating" after a road traffic accident.
In a statement, West Ham said Antonio is "currently under close supervision at a central London hospital".
The Premier League 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."
Essex County Fire and Rescue Service said it attended the scene of the accident on Saturday afternoon and released a man trapped in his car.
"Crews were called to High Road, Epping, at 1.02pm this afternoon after reports of a road traffic collision involving one car," it said.
"Firefighters reported that a man was trapped in his car and worked to release him by 1.45pm. The casualty was left in the care of the Ambulance Service."
In an earlier statement, West Ham said their "thoughts and prayers" were "with Michail, his family and friends".
Jamaica international Antonio, 34, joined West Ham from Nottingham Forest in 2015 and has since scored 68 goals in 268 league appearances for the club.
West Ham face Wolves in their next match in the Premier League on Monday (20:00 GMT).
Several clubs including Premier League sides Arsenal, Chelsea and Manchester City replied to West Ham's initial statement 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 record Premier League goalscorer.
He has scored once 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.
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.
Southampton posted their support for Antonio on X, as did Reading, Sheffield Wednesday and Colchester.
The striker has five goals in 21 appearances for Jamaica.
Former England manager Steve McClaren, now in charge of Jamaica, sent a supportive message from the Reggae Boyz.
McClaren said: "On behalf of the entire group of players, support staff and technical staff, I would like to wish Michail a speedy recovery. Our thoughts and prayers are with him at this time."