It may be more than just a cramp.
You may have torn a small amount of muscle where the strong achilles tendon attaches to the much weaker muscle fibers in the calf.
If so, it may take a period of rest to let the inflammation subside and for new scar tissue to form to join the tendon fibers back to the muscle fibers at that area.
As for the bananas, the reason players used to eat them was in part because of the misunderstanding that since bananas are high in potassium that these might help prevent cramping. It since has been shown that it is sodium (found as sodium chloride as plain old table or sea salt) is much more important than potassium in preventing cramping.
And that makes sense. The body has vast stores of potassium [lots inside every cell]. But sodium is found in high concentrations only in the blood stream. So sweating a lot [perspiration is high in sodium loss] can lead to a significant sodium loss, particularly in the heat over many hours.
That's why there is much more sodium than potassium in all the [Gatorade-like] sports drinks.
(But most cramping has nothing to do with sodium or potassium losses. It has to do with overburdening muscle tissues that have to maintain a hairspring trigger between contraction and relaxation, and overexertion can push this trigger to fire.)
Since you play a lot of tennis, and quick recovery is essential to getting the best performance out of your practice and play, you may find it worthwhile to read the following:
USTA Recovery in Tennis
http://assets.usta.com/assets/1/dps...ence/RECOVERY PROJECT 22410 EMAIL VERSION.pdf
It is a fairly quick read and covers the following:
• Nutritional Aspects of Tennis Recovery
• Heat and Hydration Aspects of Tennis Recovery
• Psychological Aspects of Tennis Recovery
• Recovery Aspects of Young Tennis Players
• Physiological Aspects of Tennis Recovery
• Musculoskeletal Injuries/ Orthopedics Aspects of Tennis Injury
• General Medical Aspects of Recovery
• Coaching Specific Aspects of Recovery
