Officers are appealing for information after the incident, which happened in Kings Street, Darlaston, at about 10pm on Saturday, May 30.
The alleged attacker left the scene in a silver car, possible a BMW.
Walsall Police posted on Facebook saying: "We are appealing for information following a nasty assault in Kings Street, Darlaston, Walsall at around 10pm on Saturday 30 May.
"It’s believed a man was walking when he was punched in the head and repeatedly kicked to the ground by another man, who left the scene in a silver car, possibly a BMW.
"The man in his 40s suffered serious injuries and required hospital treatment. He is now recovering at home.
"If you recognise him or saw the car in the area at the time, we are urging you to contact us with any information. You can contact us via Live Chat on our website or call 101. Please quote crime reference number 20WS/129411R/20/20."
Alternatively, contact Crimestoppers anonymously on 0800 555111 or at crimestoppers-uk.org