“Last year we knocked on the door. This year we pounded on it. Next year we’re gonna kick it in.”

The words of the late football coach Bum Phillips come to mind when thinking of the continuing ascension of Kei Nishikori.

Still only 24, and not yet in his prime, Japan’s highest-ranked male player ever believes he is close to breaking through in a major tournament. Just last month Nishikori beat 17-time Grand Slam winner Roger Federer for the second straight time.

“I think so. I don’t know if I am close to the top 10, but I’m playing well and won my first title this year (in Memphis in February),” Nishikori said in an exclusive interview with The Japan Times during the recent Japan-Czech Republic Davis Cup tie at Ariake Colosseum.

“It was my second time making the semifinals of a Masters 1000 (after defeating Federer). It’s getting better. It’s going well,” he commented on the state of his game.

Nishikori, currently ranked 17th in the world, defeated Federer in the quarterfinals of the Sony Open in Miami but was forced to default his semifinal against Novak Djokovic due to a strained groin.

“It (the injury) actually happened in Delray (in a tournament the week before). It was about one month ago. I’m trying to do a good rehab and fix it,” Nishikori stated.

Almost as impressive as his play this year, was the dedication he showed to his Davis Cup teammates in flying 13 hours from his base in Bradenton, Florida, to cheer them on from the sidelines.

“It was not easy to be here. I’m injured,” Nishikori said. “It was only a short time for me to try and fix my body. But this was a good experience to see my team.”

Though Japan lost 5-0 to the Czechs in its first World Group quarterfinal ever, there is little doubt that if Nishikori and Go Soeda had been healthy, the result could have been much different.

The Shimane native has suffered from injuries in the past, most notably one to his right elbow that resulted in surgery and caused him to miss most of the 2009 season. When asked if some of his ailments could be due to overtraining, he said didn’t think so and noted that the grind of the ATP Tour takes a physical toll.

“I think I am training well. The Tour is very tough,” Nishikori said. “You can’t get much time to train and rest. I have to take care of my body. When you play top guys you have to play very intense games and your body gets more damage. I think I am getting a lot of experience playing those guys, so hopefully I will have fewer injuries.”

Though practice, constant travel and playing matches are challenging, Nishikori relishes the battles that await him each week.

“With the travel you have to go to a different country every week. Then you may have to play three or four hours on the court, then again the next day,” he said. “But that is the Tour. I enjoy it. I can see many countries and have fun playing a lot of matches.”

Nishikori, who won the Memphis tournament for the second consecutive year, bested Djokovic in Basel, Switzerland, in three sets in 2011.

When asked if there was a significant match that stands out in his pro career, Nishikori cited this year’s Sony Open.

“This year in Miami I beat two top 10 guys (Spain’s David Ferrer and Federer),” noted Nishikori, who players on the Tour have referred to as “dangerous” and “tricky” after facing him.

Nishikori beat the fourth-seeded Ferrer in the fourth round after saving four match points. After downing Federer in the next match, Nishikori looked like he might have a chance to win the tournament.

The 178-cm Nishikori said that world No. 1 Rafael Nadal (who he is 0-6 against) is the player on the Tour that gives him the most trouble on court, but that he does not feel the gap between him and the elite is that wide now.

“I had a great match against Rafa at the Australian Open (where he lost in the fourth round),” he said. “I was playing really aggressive. It was a close match. I lost in three sets, but it was a close match. I feel like I am almost there to get to that level.”

Nishikori, whose highest ranking was 11th last summer, hired 1989 French Open champion Michael Chang in the offseason to help coach him.

“He is telling me a lot about his experience,” Nishikori said. “He was playing in the top 10 for a long time and he is changing my tennis, too. It has been going well.”

When did Nishikori, who has won four ATP tournaments in his career, realize he had a special talent for tennis that could take him far?

“Maybe when I was 11 or 12,” he recalled. “I won a couple of national tournaments in Japan and that is when I decided to go to the United States (where he began training at the Nick Bollettieri Academy in Florida at 14).”

Nishikori, whose best showing in a Grand Slam was in Melbourne in 2012 where he made the quarterfinals before losing to Andy Murray, looks up to the top players, but now has the confidence necessary to compete and beat them.

“I respect them a lot. Sometimes I had close matches with them,” Nishikori said. “These last couple of years I have tried to be at the same level. I think I can beat those guys. So I try to believe in myself and try to not think about the opponent and just play my tennis.”

Nishikori, who has earned more than $4 million on the court (and many more off it through endorsements with companies like Uniqlo, TAG Heuer and EA Sports), is not sure what he will do once his playing days are over.

“I don’t know yet,” he offered with a laugh. “I hope I can play for a long time — maybe 10 more years. I have not really thought about after I get done playing.”

Nishikori, with his combination of speed and shot-making, has experts convinced that a watershed showing on the big stage may not be far off.

In a 2012 interview with the Sarasota (Florida) Herald-Tribune, Bollettieri left little doubt that he believes Nishikori is very gifted.

“His movement and what he is able to do with his hands are truly unbelievable,” said the coaching legend, who helped turn Andre Agassi into an eight-time Grand Slam champion. “. . . If he stays injury-free, he can beat almost anybody.”