I would say that Sampras could take on Federer and maybe Nadal and win if it was limited set match; like a 2 out of 3 and not the 3 to 5 set match setup. Djokovic I think he could still win over Sampras
Basically, I would say that if it were a limited set matches; most of the retired pros would still be rank as a 7! The only difference is their stamina and maybe a little slower too! But definitely a 7 for Samprass, Agassi, Courier and possibly MacEnroe.
Prostaff 6.0 85, Prostaff Tour 90, KProstaff 88 Head Prestige FlexPoint 98, Head Prestige IG Youtek Mid 93.