John Isner, currently ranked No. 18, said that he doesn't worry a lot about what his ranking is.

The 30-year-old reached a career high of No. 9 in 2012. He has reached the quarterfinals at the 2011 US Open, but he has yet to reach the semifinals of a Grand Slam.

“I know where I’m ranked, but I don’t look at it that much, I don’t study it that much,” Isner told the Springfield News-Leader. “You really can’t look at it that way, you’ve got to try to win as many matches as you can, and it’s cliché, but you’ve got to take it one at a time.”

Isner has had some tight defeats in recent tournaments. At Wimbledon, the American fell 12-10 in the fifth set against defending US Open champion Marin Cilic in the third round. As the top seed at Newport on grass, Isner went down to eventual champion Rajeev Ram in the opening round, 6-7 (5), 6-3, 7-6 (8).

Isner has been working with Justin Gimelstob since the end of 2014. He said that he has been trying some new shots, but it’s not easy to change his game.

“I always have to play very aggressive on the court. It’s something that’s easier said than done,” Isner said. “When you’re out on the court, you’re fighting against yourself and it can be tough.”

This week he is the top seed at the BB&T Atlanta Open.