^ Actually static stretching prior to tennis is NOT a good idea. That is not what I meant by a proper warmup. You want a dynamic warmup when you get to the courts. That can include an easy jog or jumping jacks, dynamic stretching, shadow swings, etc. Do the static stretches at home (earlier) or after your tennis session.
If u have one foot stuck in yesterday & one foot stuck in tomorrow, u are peeing on today.