Cramp....
I get cramp sometimes which is a buggar if your under fire and trying to throw some paint back. Normally I get cramp becuase my muscles are a bit tired and also cos I'm not a young man anymore...
I cannot recomend you increase your salt intake, as their is so much salt in foods nowadays you'll only do yourself a damage, and we are all about reducing this in our diet anyway.... also if you need to supplement your diet make sure someone qualified assesses you before taking on something which long term could affect your health.
Do the simple stuff first....
On a game day make sure you graze (eat little and often) to ensure your blood sugar is maintained, and make sure you take in enough water to keep yourself hydrated. This alone will take you a long way to prevent cramp.
Stretching actually weakens the muscle for a short time after stretching, so make sure you stretch out a little before you play, and not directly before you play. The recomendation is to always stretch out before and after exercise.
Finally, having stronger muscles can prevent cramp so if you don't already, make an effort to go running, do squats, that kind of thing to build up a bit of strength and stamina.
Double finally.... if you are already a honed athlete and following the above and you still get cramp, maybe a bit of phsyio from a proper qualified phsiopherapist (spelling?) would loosen everything out.
Hope helpful....