A couple walking their dog discovered the 51-year-old man in the park at around 5.30pm on Monday.
A police spokesman said: “It’s possible he was assaulted, but police are unable to talk to him at this time to establish how he got his injuries.”
Detectives in Wakefield want to trace the couple who found him and stayed with him until the ambulance arrived. Contact DI Lester Lee at Wakefield CID on 101 with information. Or call Crimestoppers on 0800 555 111.