Marin Cilic said he believes he is in career-best form after reaching the U.S. Open semifinals.
The Croatian 14th seed was too good for Czech sixth seed Tomas Berdych on Thursday in a 6-2 6-4 7-6 (4) win at Flushing Meadows in their quarterfinal.
Cilic's semifinal appearance marks the second time he has been in a Grand Slam semi, and his first since the 2010 Australian Open.
The 25-year-old, though, refused to be satisfied too easily.
"I feel I'm playing probably the best tennis of my career. I think what helped me also was the consistent play over last five, six months," Cilic said. "This year I haven't lost too many matches against guys who are lower ranked than me. That's always very positive.
"So overall in the game I feel I'm playing well but I'm not getting satisfied too easy. I'm happy, but I still want to do well. I feel that it's still a lot to improve even in some matches. I want to keep going."