In an interview with Tennis Journal, former world No. 3 Ivan Ljubicic, who retired in 2012 and now coaches young Canadian Milos Raonic, says the difference between today’s top players and those who he started playing in 1998 -- like Pete Sampras, Pat Rafter, Michael Chang, Boris Becker, and Andre Agassi -- is commitment on a day-in, day-out basis.

“The difference between these top guys and the top guys back then are these guys are so unbelievably consistent,” Ljubicic said. “You can’t take off any point. When you played Sampras, you felt that in return games he played one or two sets, and on clay he was nowhere near his best. People actually wanted to play against him on clay. Every one of them would have parts of the season where they would lose matches and that made them vulnerable. But then again, Sampras finished No. 1 for six seasons? He had his goals and he reached them. The thing with Federer, Nadal and Djokovic is that their goal is to win every single match and that wasn’t the case with the older generation.”

Ljubicic also said he is concerned for Andy Murray’s future, as the top Briton has to return from back surgery which the Croat says is “the one [injury] you don’t want.”

The Croatian also believes that No. 11 Raonic will soon to begin to threaten the Top 5 players.

“That’s the goal, not tomorrow but sometime next season,” he said. “If things progress the way we hope, he’s going to get closer. It’s no secret he’s not there yet and there’s a lot of work to be done, but he’s 22 and I have no doubt he will be up there.”