Grigor Dimitrov reaches his 1st Grand Slam quarterfinal at Australian Open

Grigor Dimitrov of Bulgaria hits a backhand return to Roberto Bautista Agut of Spain during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aijaz Rahi) (The Associated Press)

Roberto Bautista Agut of Spain hits a backhand return to Grigor Dimitrov of Bulgaria during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aijaz Rahi) (The Associated Press)

MELBOURNE, Australia – Grigor Dimitrov has advanced to his first Grand Slam quarterfinal in his 14th attempt after beating Roberto Bautista Agut 6-3, 3-6, 6-2, 6-4 at the Australian Open on Monday.

Dimitrov, who beat No. 11 Milos Raonic in the third round, will play either top-ranked Rafael Nadal or Kei Nishikori in the last eight on Wednesday. He clinched the match by breaking Bautista Agut's serve for the fourth time.

The 22-year-old Bulgarian's breakthrough win came on the same day his girlfriend, Maria Sharapova, lost her fourth-round match to Dominika Cibulkova.