Federer and Nadal still the top men, but Zverev and Shapovalov have given next generation hope

It might not have been what Roger Federer or Rafael Nadal would have wanted themselves, but the triumphs in Montreal of Alexander Zverev and Denis Shapovalov was what men's tennis desperately needed.

Zverev gave Federer only his third defeat of 2017 in Sunday's Canadian Open final, and Shapovalov delighted the home crowd when he came from a set down to beat Nadal in the third round on Thursday.

Now 2017 has been a lot of fun in terms of nostalgic value, watching the respective renaissances of Federer and Nadal as they have returned from injury to dominate the game and one of them is guaranteed to replace Andy Murray as world No 1 next week.

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[ Novak Djokovic out of the rest of 2017 action with an elbow injury ]

But Federer turned 36 last week and Nadal is 31, and while the pair's reputation as two of the greatest ever to play the sport is already cemented in the history books, it does beg the question of just when are the next generation of superstars going to arrive to kick on and take centre stage?

Zverev has been on the radar for some time and defeating Federer 6-3, 6-4 on Sunday was a fresh reminder that the German does look as if he has the potential to kick on.

He beat Nadal to win the Italian Open in Rome in May and claim his first ATP Masters title, and now he has proven he can more than hold his own against Federer in a big-match environment as he won a fifth tournament of 2017.

The win puts him up to No 7 and he is almost certain to be seeded at No 5 or higher at the US Open later this month, with two of the men above him in the standings, Novak Djokovic and Stan Wawrinka, both having already ruled themselves out of the action in New York due to injury, and Murray also a doubt.

It was not just the power and accuracy of Zverev's play in beating Federer, who had won his previous 16 matches, and all in straight sets, that impressed.

His maturity and poise really stood out. He looked like he belonged, and more importantly it came across that he believed he belonged.

His biggest test now is consistency. After beating Nadal, which was the Spaniard's only loss during his excellent clay court season of action, Zverev subsequently crashed out in the first round of the French Open later that month to Fernando Verdasco.

He has never been beyond the last 16 at a grand slam, and now he has proven he can beat Federer and Nadal, it is now about bringing his best to a major, and whether he can do that at Flushing Meadows will be one of the interesting narratives.

Unlike Zverev, Shapovalov, 18, was not on the radar, well at least not to upset the top seed and world No 2.

The Canadian was only in Montreal as a wild card, but he defeated Juan Martin del Potro and Nadal on his way to the semi-finals, where he went down to Zverev.

The teenager played superbly to beat Nadal and he highlighted the Spaniard's fallibility at the back of the court by consistently out-lasting him in rallies, and then holding his nerve in the final set tie-break.

The test for Shapovalov is to build on it and ensure it is not a false dawn, and that he can establish himself in the top 20.

Tennis is going through an interesting period, with Djokovic, Murray and Wawrinka, the three men to win majors in 2016, all struggling with injuries.

There are gaps to be exploited at the top of the game right now. Yes, it is Federer and Nadal at the top right now, but both men are in the twilight of their careers, and while they may both be doing their best to disprove it, neither can go on forever.

The top five are all over 30. Tennis is no longer a younger game as sports science and better understanding of fitness and dieting means players are now beginning to play longer into their thirties, and remain competitive while doing so.

But, wear and tear has caught up with all five of them over the past year, and while the immediate focus is on the Cincinnati Masters this week and who out of Federer and Nadal will become world No 1, Zverev and Shapovalov have brought some fresh intrigue to the sport.

They have shown it might be sooner rather than later before the next generation come through, and that it is not a foregone conclusion that it will be Federer and Nadal dominating in New York.