Nishikori confident after success in Australia

Now that he's had success on one of tennis's biggest stages, Japan's Kei Nishikori is determined to take his game to the next level.

Nishikori last month became the first Japanese man to reach the quarterfinals of the Australian Open since the Open Era began in 1968 with a 2-6, 6-2, 6-1, 3-6, 6-3 victory over former finalist and sixth-ranked Jo-Wilfried Tsonga of France in the fourth round.

The 22-year-old lost to No. 4-ranked Andy Murray in straight sets in the quarterfinals but said his success in Melbourne has given him the confidence to take on the world's top players.

''I was aiming to reach the quarterfinals and to beat a top-10 player in a major tournament like the Australian Open gives you a lot of confidence,'' Nishikori said on Monday in an interview with The Associated Press.

Nishikori also matched the best Grand Slam performance by a Japanese male in the Open Era - Shuzo Matsuoka's run to the quarterfinals of Wimbledon in 1995. His quarterfinal finish took him to a career-high 20th in the world rankings.

Nishikori moved to the United States at the age of 14 and attended the Nick Bollettieri Academy in Bradenton, Florida. It was a bold move considering he didn't speak a word of English but one that paid off.

At the age of 18, he won at Delray Beach to became the youngest man to win an ATP title since Lleyton Hewitt captured his first in 1998 at 16.

''Moving to the United States allowed me to play against a lot of different players,'' Nishikori said. ''I was able to get stronger as a player and felt that the world wasn't as far away as I thought.''

After hiring Brad Gilbert as one of his coaches at the end of 2010, Nishikori finished last season with a flourish. He reached his first Masters semifinal at Shanghai and finally broke Matsuoka's mark, rocketing all the way up the rankings to No. 24 after upsetting world No. 1 Novak Djokovic to reach the final of the Swiss Indoors.

''I had a hard time believing I was able to beat a player like Djokovic,'' Nishikori admitted. ''He was having an incredible year and beating the world's No. 1 player proved to me that I was getting better. It was definitely a result that helped me to do well in Australia.''

Nicknamed ''Air K'' because of the jump he takes to give his forehand a little extra power, the 1.78-meter (5-foot-10) Nishikori said the move was designed to make up for a lack of height. ''I don't remember when I started that but it was when I was very young. I knew I wasn't that tall and this was one of the ways I tried to compensate for that.''

Nishikori was given a quick reminder how tough tennis can be when he lost to big-serving Ivo Karlovic in the Davis Cup World Group series on Friday. Croatia went on to beat Japan 3-2 and Nishikori, who won his reverse singles match on Sunday, blamed himself for the loss.

The 2.08 meter (6-foot-8) Karlovic is 43rd in the rankings but his powerful serve allowed him to record 18 aces in his 6-4, 6-4, 6-3 win over Japan's top player.

''I've never played a guy like him before,'' Nishikori said. ''Fortunately, there aren't too many like him on the tour and next time I meet a guy like that I just have to try to stick to my style of play.''