Heavyweight coaches ready to lock horns in semis

Michael Chang versus Boris Becker and Goran Ivanisevic up against Stefan Edberg would have made an intriguing U.S. Open semi-final line-up when they were in their prime.

On Saturday they will go head-to-head as the respective coaches of the four men to reach this year's semi-finals.

While Ivanisevic will not be able to deliver any of his booming aces, Chang chase around like a hyper-active terrier, Edberg swish away effortless backhands or Becker launch himself through the air to pick off volleys - their mere presence will add another dimension to the drama.

Becker will be masterminding world No.1 Novak Djokovic's attempt to reach a fifth consecutive U.S. Open final by beating Japan's Kei Nishikori, who since adding former French Open champion Chang to his team has emerged as genuine major threat.

Towering Marin Cilic will have fellow Croat Ivanisevic in his corner as he attempts to reach his first grand slam final by beating Swiss maestro Roger Federer who has been rejuvenated since tapping into Edberg's serve-and-volley skills.

So what effect have the four greats had on their charges?

BECKER/DJOKOVIC

There is little in common with the way German powerhouse Becker served-and-volleyed his way to six grand slam titles and how Djokovic has managed seven with clinical baseline precision.

Eyebrows were raised when Djokovic announced last December that Becker would join his team alongside long-term coach Marian Vajda, and the early signs were not encouraging as he lost to Stanislas Wawrinka in the quarter-finals of the Australian Open.

Since then, however, the Serb won the Indian Wells/Miami double on hard courts, beat Rafa Nadal in the final in Rome and then reached the French Open final before winning Wimbledon for the second time by defeating Federer in an epic.

While there are no obvious changes to the Djokovic style, there is a little more variation on his serve and he appears more confident around the net. Most of all, though, he seems to enjoy having one of the game's big personalities on his side.

"I'm a different player than what he was in terms of play," Djokovic said at Wimbledon. "But in terms of mental approach and other things, I find that we have a lot of things in common."

In a recent interview with CNN, Becker said Djokovic reminded him of his young self, fighting against players who perhaps enjoyed more crowd support.

"I was known to be a pretty hard-nosed guy on court with a very strong mentality," Becker said. "I was a fighter's player."

FEDERER/EDBERG

There is nothing anyone can teach 17-times grand slam champion Federer but as his physical powers wane, Edberg has given Federer the confidence to employ more attacking tactics.

Federer enjoys nothing more than playing on the front foot but in recent years has occasionally became a little passive against the likes of Djokovic, Nadal and Murray.

Not the most powerful, his serve still has the most variety in the men's game and Edberg, one of the greatest serve-and-volleyers to grace the sport, has encouraged Federer to follow it in more for a quick finish to points. And it's working.

"Maybe (he) just reinforced the concept that it is possible, that I can actually do it," Federer said this year. "For years I started to serve and volley once or twice a set maybe."

NISHIKORI/CHANG

Long talked about as one to watch, Nishikori has added a little Chang-like steel to his shot-making skills.

Chang was a master at making every point a war of attrition and while Nishikori is a more flamboyant player, he has clearly become much better on the defensive skills that the likes of Djokovic, Nadal, Federer and Andy Murray possess.

His five-set quarter-final win against Stanislas Wawrinka would have made old warrior Chang proud.

The 24-year-old is the first Japanese man to reach a grand slam semi-final and though Djokovic presents a formidable obstacle, Chang believes he will not be daunted.

"He's beaten Novak before. There's no reason why he's not able to do it again," he said.

CILIC/IVANISEVIC

After serving a four-month doping ban last year for taking a tainted supplement, Cilic has returned with new purpose and looks a much more confident character on court.

The 25-year-old has always possessed big weapons but occasionally appeared to lack belief against the big guns.

Ivanisevic's infectious good humor and personality is having a galvanizing effect, as his demolition of Tomas Berdych on Thursday showed.

"It's a nice combination," Cilic, who stretched Djokovic to five sets in the Wimbledon quarter-finals, said. "He's eager on the court when we are working on things, and of course the other part where he's calm in certain other situations.

"That's huge confidence for me when I come step on the court."

(Reporting by Martyn Herman, editing by Pritha Sarkar)