I would assume this is outdoor environment (those Sports Council type) depending on the side "lamp post" lights.
Depending on where your tennis court is, you may not be able to stand near to them (I wouldn't want to anyway....tennis ball are fast and hard) and you may need to utilize the mid (100mm)-far end of the lens which the max aperture is f4.5 to f5.6 (which is quite-very slow at night)
I can only say that the Shutter speed depends on the type of effect you want for your shot. E.g. freeze motion with the tennis ball freezing infront of the tennis racket while swinging or some motion blur when swinging the racket etc.
Based on my limited experience with "freezing" movement with this lens at night at long focal length (wide open at f4.0 or at f5.6), you will be using 1600-3200 or higher all the time no matter 1/100 or faster 1/250 >.
My recommendation, set your ISO to your max tolerance of high ISO (for my 500D, ISO1600 is my max tolerable, not sure about yours). and start shooting at whatever shutter speed you want. Your camera will most probably be keeping the aperture wide open. Also, do keep in mind, that high iso = more noise.