Personally I'd feel like Djokovic is one that sticks out to me. Career quitter to tour iron-man who actually gets quicker and stronger the longer the match goes!!!
I say Nadal as well. Not currently but in the past which is why he has so many continual health problems today. I know his medical problems are not an effect from doping but I do believe his medical problems were suppressed by doping in the past.
Racquet: Wilson 6.1 95s String: ISOSPEED Baseline Control 16 @50lbs in mains, Random multi/syn gut @55lbs in crosses