World No. 1 Novak Djokovic will take on No. 4 Andy Murray for the ATP Cincinnati Masters title, Djokovic advancing in an abbreviated semi-final after Murray battled his way through.

Murray held off top American Mardy Fish 6-3, 7-6 (10/8), while Djokovic had just taken his opening set against Tomas Berdych 7-5 when the eighth-seeded Czech retired with a right shoulder injury.

Djokovic claimed his 57th match victory of the season, with just one defeat. On Sunday he’ll be gunning for his 10th title of 2011 and a sixth prestigious Masters title this season.

Murray, meanwhile, will be seeking just his second title of the year, after his triumph on the grass courts of Queen’s Club in June.

“I think it would be perfect preparation to play him before the US Open, to see what I need to work on,” Murray said of a clash with the game’s dominant player.

The Scotsman cruised through the first set against Fish, but then found himself in a battle in the hot, humid weather.

Murray, who was bounced in his opening match at the Montreal Masters last week, held on to win in 2hrs 18min - capturing the tiebreaker after the two had exchanged six service breaks in the second set.

He seemed to be feeling the effects of the physical encounter as he massaged the back of first one left leg and then the other.

“My legs were feeling tired. It was the conditions. I need to get stronger. This is the first tough match I’ve played for five or six weeks. I need to get some more endurance in me before the US Open.”

“I was struggling physically in the second set, it was hot but that’s not an excuse,’ said Murray.

Fish, meanwhile, appeared to be favouring a sore heel that has bothered him earlier this season.

However, the American insisted the uncomfortable ailment “did not affect the outcome of the match”.

After the rash of service breaks, Fish fended off a triple break point in the 11th game of the second set.

Murray then saved two in the 12th game to force the tiebreaker, in which Fish had a chance to claim the set before Murray captured the match on his third match point.

Murray appeared to have won the match with a service return winner for 9/7 in the tiebreaker.

Fish challenged the call, but was already walking toward the net when the replay showed Murray’s return was out by a hair.

“I was really surprised,” Fish said.

Two points later, however, Murray put it away.

Djokovic needed no second-set dramatics - or indeed any second set.

Berdych had said he wasn’t at full strength after hurting his shoulder in his quarter-final upset of two-time defending champion Roger Federer.

He still managed to gain an early break and lead 5-4. But he was clearly fading as he dropped his serve with a double-fault to let Djokovic knot the set at 5-5, and after Djokovic broke him again to win the set Berdych called it a day.

“In the beginning, it was so-so and I was able to hit a few balls,” Berdych said. “But when the match was going more and more, it was just worse and worse. There was no chance to serve.”

Djokovic, who also played with tape on his right shoulder, called the abrupt ending “unfortunate”.

“I know he struggled a little bit with a shoulder injury. We have a similar thing, he just has a more serious injury,” the Serbian said.

“Playing that many matches and having a busy schedule is taking a toll on not just mine but on all players’ condition,” he said. “It’s normal. You’re out there trying your best as Tomas did today.”

In the women’s semifinals, world number two Vera Zvonareva will meet fourth-seeded Maria Sharapova in an all-Russian affair and ninth-seeded German Andrea Petkovic will take on former world number one Jelena Jankovic of Serbia.