WHAT'S the difference between personal love and tennis love?
That is the riddle Bulgarian Grigor Dimitrov spent years trying to crack and it appears he may have solved it.
After bursting on to the ATP Tour as a young man with the nickname "Baby Fed", Dimitrov was involved in some high-profile relationships with his WTA counterparts.
He initially dated Serena Williams before going on to start a relationship with Maria Sharapova, which ended in mid-2015.
But did these relationships have an impact on his potential rise up the rankings as a young man?
"I obviously have a soft spot for that," he grinned.
"You know, on a serious note, I always try to keep whatever else outside the court. I think when I was younger, I was struggling to kind of differentiate love from a personal love or a tennis love or whatever else, for sure."
Dimitrov has enjoyed an amazing start to his 2017 season, with the 25-year-old yet to lose a match and into the Australian Open quarter-finals.
He said he had learned how to balance his tennis with the "falling-in-love stuff".
"You know, there was time, a period, that I wasn't, like, kind of sure how to deal with both things in the same time. But you learn. I guess we grow," he said.
"I mean, I don't want to say I've learned from my mistakes, but I've learned myself a little bit better. I think that helps me. Hopefully it's going to help me for the future through any kind of falling-in-love stuff."
Dimitrov has since dated American singer-songwriter Nicole Scherzinger.
Scherzinger was a member of the Pussycat Dolls and has recently been an X-Factor judge.
Dimitrov, the 15th seed, takes on 11th-seeded Belgian David Goffin on Wednesday.