I have this player who is 27 years of age, very competitive and driving complete player with great technique on his ground stokes. Basically a great all around player from the baseline and net. I want to challenge him with a intense footwork drill that will tire him out, yet get the necessary hitting time. The more intense and sweat the drill produces the better, I'm the kind of coach where footwork is the basic foundation for all tennis players. I'm open to any suggestions, thank you for your time.