A member of the public found the man in a wooded area of Three Bridges Recreation ground at around 8am.
The man had sustained wounds to his leg and buttock and was taken to hospital for treatment.
He remains in hospital in a serious but stable condition. His injuries are not thought to be life-threatening.
It is not yet known how the man was injured.
A section of the field has been cordoned off to enable forensics investigations to take place, and to determine whether any offences have been committed.
Anyone with any information which could be relevant to the incident is urged to report it online or call 101, quoting serial 423 of 20/06.
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Man found injured in Three Bridges Rec, Crawley. SUS-210620-123138001 Photo: eddie mitchell
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Man found injured in Three Bridges Rec, Crawley. SUS-210620-123150001 Photo: eddie mitchell
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Man found injured in Three Bridges Rec, Crawley. SUS-210620-123201001 Photo: eddie mitchell
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Man found injured in Three Bridges Rec, Crawley. SUS-210620-123051001 Photo: eddie mitchell