Thank you for the query.
Hard calf, painful while pushing it, warmer than the calf on the other side can be a symptom of veins thrombosis. It could be triggered by some trauma during the game (even if you have not noticed it as a trauma).
There is a symptom you can check at home. Please have your leg straight in the knee while sitting and flex your foot down. If it causes the pain radiating to the knee, veins thrombosis is probable (however lac of this sign does not rule it).
Other reason of your pain can be strained muscle.
I suggest you to visit your doctor (veins thrombosis can be urgent condition as it can cause pulmonary thrombosis
) and have blood work, D-dimers level and if elevated, Dopplers ultrasound
should be performed.
Hope this will help.