Officers said the collision involved a red Ford Fiesta and a 52-year-old man on the A643 at around 4.50pm yesterday.
West Yorkshire Police said: "A male pedestrian has sustained serious leg injuries and other superficial injuries after being struck by the vehicle.
"It is requested that if there are any witnesses to the collision to contact the police."
Leeds United fans took to social media after the club's 1-0 win over Brentford to discuss the "sad news" of what happened outside the stadium.
Officers then released a statement shortly after midnight.
Inspector Darren Brown, of West Yorkshire Police, today said that officers initially responded to a report of a man having a head injury, but he had actually broken his ankle.
The man was treated in hospital.
LUFC owner Andrea Radrizzani today tweeted: “Thank god the injuries to [the] fan in [an] accident outside the ground are not as severe as first suggested. “Still very painful, stays in our prayers. Get well soon!”
Police are also requesting that if any drivers in the area at the time had "dash-cam" footage, or saw "the manner of the vehicle being driven", to make contact on 101 and speak with PC 6042 GIBSON, quoting collision reference 1318009269.