A tear of the Achilles tendon is a relatively uncommon injury in sport and could be very dramatic when it occurs, because the calf muscles and the connected Achilles tendon play such an crucial function. It is more likely to occur in explosive activities like tennis. The real issue is that the achilles tendon and the two muscles attached to it cross two joints (the knee and the ankle) and if the two joints are moving in opposite directions simultaneously, especially if instantly (as might happen in tennis), then the likelihood of something going wrong is quite high. 
The management of an achilles tendon rupture is a bit controversial because there are two alternatives that almost all the research shows have got virtually identical outcomes. One option is conservative and the other is operative. The conservative option is typically putting the leg in cast that holds the foot pointing downwards a little. Usually it takes as much as six weeks to heel up and after the cast is removed, there should be a slow and gentle resumption of exercise. Physical rehabilitation is usually used to help with this. The surgical choice is to surgically stitch the two ends of the tendon back together, this is followed by a period in a cast that is shorter compared to the conservative choice, and will be followed by a similar steady and slow return to activity. When longer term outcomes are evaluated the final result is generally about the same, but the surgical method has the added chance of surgical or anaesthetic complications which the conservative method doesn’t have. The choice as to which approach is better for an achilles tendon rupture is going to have to be one based on the experiences of the surgeon and the preferences of the individual with the rupture. There’s a trend for competitive athletes to go down the surgical pathway since it is considered that this will give a better short term outcome and get the athlete back to the sports field quicker.