NEW YORK (AP) - In front of a sparse crowd at Louis Armstrong Stadium, Andy Murray didn't quite feel as though he was playing in a Grand Slam quarterfinal.
And Murray wasn't exactly playing like an Olympic gold medalist.
Then the crowd started to filter in, the court started to slow down in cooling temperatures and - probably most importantly - Marin Cilic started to get tense. A point away from going down two sets, the third-seeded Brit rallied then rolled for a 3-6, 7-6 (4), 6-2, 6-0 victory Wednesday.
"He got nervous. That was the main difference,'' Murray said. "I did start playing better towards the end of the second set. And because I was in it, I started to feel that momentum was with me.
"It wasn't necessarily through my great play in the second set why I got back into it. But after that, I was hitting the ball much better, and I felt confident at the end of the match. I was returning well, serving well, and moved better at the end. It was good to finish like that, obviously.''
A surprise finish in the next quarterfinal changed the terrain of Murray's road to a first career Grand Slam title. Peppered with questions about a potential rematch with Roger Federer during his news conference, Murray - who was sneaking glimpses of the score of Federer's matchup with Tomas Berdych - reminded everyone to respect the Czech.
He was right. Berdych upset Federer to become Murray's semifinal opponent.
Murray had trailed 5-1 in the second set before breaking twice to come all the way back. In the tiebreaker, Cilic had a 4-2 lead and a point on his serve. Murray erased the mini-break with an easy forehand passing shot, running off five straight points to even the match.
With royal in-law Pippa Middleton in the crowd, he won the last 11 games to wrap up the victory in 3 hours.
Cilic, seeded 12th, was seeking his first U.S. Open semifinal berth. The Croat had a set point at 5-2 in the second, but Murray hung in throughout a 14-shot rally and put the point away with a soft backhand volley into the open court.
"Those kind of guys like him at the top, you can't let them come back,'' the 23-year-old Cilic said. "He's not going to give me another chance.''
Cilic got in 70 percent of his first serves in the opening set - that number dropped to 45 percent in the second and third.
"I was more aggressive on his second serve,'' Murray said. "I started serving better and then gained confidence in my shots from the baseline, because the first set, set and a half, I was leaving the ball short and wasn't timing it well. He was able to dictate all of the points.''
Two days of rain delays resulted in this quarterfinal switching from Ashe to Armstrong - with few spectators in the stands at the start. Murray has never felt particularly comfortable in the Open's second-largest stadium. He thinks it has something to do with the close walls, the swirling winds and the fast court.
In the third round, in Armstrong, he had to win three tiebreakers in a four-set victory over Feliciano Lopez. But in Arthur Ashe Stadium for the fourth round, Murray routed Milos Raonic in straight sets.
Good news for Murray: They play the semis and final on Ashe.
The victory also clinched Murray a spot in the season-ending ATP World Tour Finals in London.
Cilic fell to 1-7 against Murray - though that one win came at Flushing Meadows, in the 2009 fourth round in straight sets. Incidentally, that match was on Ashe.
A 2010 Australian Open semifinalist, Cilic was starting to run out of energy by the fourth set Wednesday. He pulled out five-set wins in the first two rounds here - rallying from two sets down in his opening match. He then had a four-setter on a blisteringly hot day.
Cilic was able to chuckle about how a shaky start turned into a confidence-building run at this year's Open, considering that two sets into the tournament, "I was looking for already my flight tickets to go back home.''
Murray is sticking around until at least Saturday.