Japan's Kei Nishikori defeated world No. 4 Grigor Dimitrov in three sets on Wednesday to advance to the third round of the Italian Open.

Nishikori, ranked 24th in the world, lost the first set in a tie break before coming back to beat the third seed 6-7(4), 7-5, 6-4 in two hours, 55 minutes. With the second set even at 5-5, Nishikori fired his only ace of the match to hold serve and then broke the Bulgarian to even the match at one set apiece.

Earlier, an out-of-sorts Naomi Osaka offered little resistance to world No. 1 Simona Halep, lasting just 59 minutes in a 6-1, 6-0 second-round drubbing.

The 26-year-old Romanian, who fell to eventual champion Osaka in the semifinals of the BNP Paribas Open in March, lost the opening game of the match before reeling off the next 12 to take revenge in emphatic fashion.

In what was clearly an off day for the Japanese world No. 21, Osaka hit 29 unforced errors while managing just 10 winners. Halep, meanwhile, hit only 14 unforced errors and took 80 percent of points from Osaka's second serve.

Down 5-1 and facing three set points, Osaka threw her racket to the ground in frustration. The 20-year-old then barely moved her feet as Halep hit a backhand winner at 15-40 to wrap up the first set in just over half an hour.

The second set was an even briefer affair, with Osaka appearing to capitulate before quickly exiting the court.