Let's be honest here, none of the "big four" today rank high in this category, and the haters of each can all supply quite valid reasons as to why.
So let us examine some players throughout history who emanated masculinity to the core:
Marat Safin - This is as obvious as saying the sun is bright. Huge game, allergic to pushing, hot-tempered, openly and proudly displayed his many groupies, square-headed and broad-shouldered. A TW favourite.
Jimmy Connors - Didn't have a huge game, but compensated with his longevity and belligerence. Laid the smackdown on crybaby extraordinaire John McEnroe and never receded from visually referencing his manhood to the fans.
Pete Sampras - You knew this was coming. The slam dunk smashes say more than words ever could. Refused to grind/push, would tank unneeded return games. Massive serve, gorilla-like posture but with chest hair said gorilla could only envy.
Carlos Moya - When you picture masculinity in your head, you can't say that Carlos Moya's image doesn't occur. Thus far the only player to adopt the sleeveless get-up and retain respectability. If I needed a tennis player to pull me out of a burning building, he'd be the guy I'd call.
Goran Ivanisevic - Yes, there are some significant minuses here on account of his habitual choking, crying and double faulting, but at the same time, he is the last grand slam winner with facial hair. Also, gigantic serve.
Marcelo Rios - This is a guy, who, if his Wikipedia page is accurate, didn't take "guff" from anybody. He ran over his trainer with a Jeep, threw his wife out of a moving car, punched a taxi driver in the face and attacked the arresting officer, urinated on patrons in a Chilean bar and "allegedly" told Monica Seles to move her "fat ***" while in line for lunch. Case closed.
Ivo Karlovic - In pure animalistic terms, this guy is your true winner. In any mating competition, Karlovic would be the alpha by default. Quite simply, he's bigger, and therefore better, than everybody else.
Who else?
