NEW YORK: Second-ranked Andy Murray was knocked out of the US Open by Marin Cilic of Croatia in a lopsided 7-5, 6-2, 6-2 fourth-round loss on Tuesday.

Cilic overcame two set points in the first set, then pounded Murray over the last two to reach his first career Grand Slam quarter-finals. Murray, who lost to Roger Federer in the final at Flushing Meadows last year, will finish 2009 without making a major final.

Murray will slide back to No 3 or No 4 in the rankings, behind Rafael Nadal, who will move up by virtue of beating No 13 Gael Monfils of France 6-7 (3), 6-3, 6-1, 6-3 to get to the quarter-finals. Nadal-Monfils featured two men often cited as the best athletes on tour, and it was a spirited contest early, filled with long points, terrific retrieving, powerful hitting — and animated celebrations by both. Monfils eventually began to show signs of fatigue, leaning over to gasp for air between points, and Nadal took control.

Nadal, trying to complete a career Grand Slam by winning the US Open, will meet No 11 Fernando Gonzalez of Chile next. Gonzalez eliminated No 7 Jo-Wilfried Tsonga of France 3-6, 6-3, 7-6 (3), 6-4.

Cilic moved on to meet sixth-seeded Juan Martin del Potro, who reached his second straight US Open quarter-finals by cruising past No 24 Juan Carlos Ferrero 6-3, 6-3, 6-3. Cilic vs del Potro will pit two players who are 20, with lanky frames and big serves.

Cilic said the set points he saved, serving at 4-5 in the first, were the turning point against Murray. He responded by getting ahead 0-40 on Murray’s serve in the next game, won the second break point, then took 13 of the next 17 games for his first career win over an opponent ranked in the top three. Murray had 29 unforced errors, 12 fewer than Cilic, but he hit only 13 winners and never looked comfortable in the match.

On the women’s draw, Kim Clijsters, already into the semi-finals, will face a Williams for the second time in this tournament. Clijsters beat Venus Williams in the fourth round; now she’ll take

on defending champion Serena Williams, who improved her win-loss record to 23-1 in Grand Slam singles this season by beating No 10 Flavia Pennetta of Italy 6-4, 6-3.

The American and Belgian both have 12-match winning streaks at the US Open. Clijsters won the first seven en route to the 2005 title, the last time she played in New York, and has five this year, the last a 6-2, 6-4 win against 18th-seeded Li Na of China. Still unranked because she only had played in two tournaments before the US Open, Clijsters is the first unseeded woman to reach the semi-finals at Flushing Meadows since Elena Dementieva in 2000.