Lleyton Hewitt continued his build up for this month's U.S. Open by winning a battle of former world number ones with a 6-4, 6-4 victory over Marat Safin in the quarter-finals of the Cincinnati Masters.

The Australian 10th seed beat the 24-year-old Russian in a contest on Friday containing plenty of brilliant counter-hitting and a little controversy.

"I played pretty well on his service games," said Hewitt, the 2001 U.S. Open winner.

"I feel like I have been playing pretty well this year... I feel that I am near the mark. I just hope that in a few weeks time I will get the breakthrough."

Safin had the greater weight of shot but was eventually frustrated by Hewitt's consistency and superior mental toughness.

When a Hewitt drive, which appeared to land a couple of inches out in the second game of the second set, was called in, Safin reacted with anger.

He squatted on the court, placed his fingers on the surface to show the distance by which the ball had missed, and walked up to the umpire to remonstrate.

The decision appeared to distract Safin as he lost four successive points to drop the game, which allowed Hewitt to take a firm grip on the match.

Earlier, Safin had also picked up a code violation warning after smashing his racket in frustration.

To add to his woes, the unpredictable Russian was also hindered by his troublesome wrist, which he had taped by an ATP trainer.

"It's important for me to get confidence and to keep it as long as I can," he said sorrowfully.

"Then I can squeeze everything from that."