Top seed Rafael Nadal kept his hopes for the tennis season's seventh title alive here in the ATP Shanghai Rolex Masters, defeating Grigor Dimitrov of Bulgaria in a high-quality 6-4, 6-7(4), 6-3 game on Friday to set up a semi-final clash against Croatian Marin Cilic .With this second victory over Dimitrov in as many weeks, the Spaniard also extended his winning streak to 15 matches since his third-time US Open success, reports Xinhua news agency."It was a very tough match. I think both of us, we played at a very high level of tennis. The conditions, of course, have been different today than the two previous matches," the Spaniard said after the match."It was the first match for me outdoors, so is a different story, but at the same time, I enjoyed. I think it was a great battle between two players who are playing all the time very focused."The second set was a close one as both players held all of their six serves and had to fight in the tie-break. It was the sixth seed Dimitrov who produced a better performance, powering to win 5 consecutive points at 4-2 to close the tie-break 7-4 and levelled the set-score."It's true that at the end of the second, that tie-break, I made a couple of mistakes with the forehand. I made bad decision going for the forehand in the 4-2 of the tie-break. I should hit that ball with the backhand, but I decided to go with the forehand before he hit the ball. And then, two good serves for him, 5-4," the 31-year-old world no.1 Nadal said.But Nadal, striving for his maiden title in Shanghai, regained his form in the deciding set, broke the Bulgarian's service in the sixth game to take a 4-2 lead and eventually closed the two-hour and 32 minute battle with a 6-3 decider win.Earlier in the afternoon, fourth seed Cilic knocked out Albert Ramos-Vinolas with a straightforward 6-3, 6-4 victory.Swiss superstar Roger Federer will play against Frenchman Richard Gasquet at the Qizhong Stadium later on Friday to fight for another spot in the semi-finals.