Maria Sharapova's ex-boyfriend Grigor Dimitrov admitted his relationships may have delayed his emergence as a top player as he extended his hot streak at the Australian Open on Monday.

The Bulgarian heart-throb has long been touted as one of tennis's next big things, but he reached only his third major quarter-final with his win over giant-killer Denis Istomin.

Dimitrov, 25, beat the injury-hit Uzbek 2-6, 7-6 (7/2), 6-2, 6-1 to reach the last eight and stretch his winning streak to nine matches after he won this month's Brisbane International.

Afterwards, the man known as "Baby Fed" for his Roger Federer-style play was asked whether romantic entanglements may have sometimes been a distraction from tennis.

"I obviously have a soft spot for that," joked the world number 15. "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 differentiating love from a personal love or a tennis love or whatever else. There was time that I wasn't sure how to deal with both things in the same time.

"But you learn. I guess we grow. 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, who split with Russian star Maria Sharapova in 2015, will face Belgian 11th seed David Goffin for a place in the semi-finals in the lower half of the draw.

Istomin, the bespectacled world number 117, showed the effects of a demanding tournament following his sensational second-round upset of six-time winner Novak Djokovic.

His game deteriorated after losing a second-set tiebreaker and despite medical treatment, he had trouble getting around the court as Dimitrov charged to victory.

Dimitrov lost to Rafael Nadal in the quarter-finals in Melbourne three years ago and last year he fell to Federer in the third round.

Dimitrov also reached the semi-finals at Wimbledon in 2014 where he lost to Novak Djokovic, after defeating defending champion Andy Murray in the quarter-finals.

Istomin, who qualified via the Asia wildcard play-off, beat Ivan Dodig and Pablo Carreno Busta, as well as Djokovic, to reach the fourth round, equalling his best Grand Slam result.

"It's an unbelievable feeling. I'm not lying. I'm happy to be on that stage of a tournament. Quarter-finals of a Slam, it's great," Dimitrov said.

"I'm happy that I'm capable to do that. Just looking forward to the next one."

Source :AFP