Up to 60 people, some armed with weapons, were understood to have gathered off Stratford Road, Sparkhill just before 9pm on Friday.
After trouble 'flared up' a 26-year-old was taken to hospital with stab wounds which were fortunately not serious and a 23-year-old man suffered a suspected fractured eye socket.
Four other men - aged between 27 and 52 - suffered injuries which were not serious.
Police recovered a knife, a hammer and a chain from the park. They are being examined for clues to establish who was involved in the violence.
Officers will also be upping their visible patrols in and around the park over the weekend, while deploying special stop and search powers on a temporary basis.
Section 60 powers mean that police can stop and search people they "suspect may be involved in violence, involving weapons, without the need to have reasonable grounds."
A police statement added: "We'll also have S60 powers available from now until 11.59pm today ... We don't use S60 powers lightly but we must do all we can to reduce the risk of further disorder.
"Our priority is to protect the public.
"Anyone with information is asked to contact us via Live Chat on our website and quote 20/723158/22. Alternatively ring the Crimestoppers charity on 0800 555 111."