Monfisl and Djokovic are getting distant balls coz of stretching abilities imo and the fastest i think is Nadal.
He's a good short distance sprinter imo, yet a bit rigid (also perhaps coz of extra muscles)
this;:::: Djokovic is extremely flexible and slides wonderfully on all surfaces but he certainly isn't the fastest. Novak probably has the best balance and can twist his body around the best of anyone
I do however think Monfils would be in the running with Nadal still