There are some things in tennis that sound almost improbable. Beating Roger Federer and Novak Djokovic in straight sets on successive days, in the semi-finals and finals of a major tournament ranks high in this list.

But 21-year-old Alexander Zverev did just this to win the season-ending ATP Finals on Sunday. No better way to lift your biggest career trophy, right?

The German became the youngest winner of the season finale since Djokovic himself in 2008. At a time when he could well be playing the ATP NextGen finals in Milan (he had qualified both years but chose London), Sascha, as he is called, is making a much-needed case for his generation.

For the last two years, anyone who has regularly watched Sascha play will attest to the fact that he is indeed the future of men’s tennis. Of course, the trope of “men’s tennis future” is almost a running joke by now.

In the highest echelons of the ATP World Tour, age is not a factor. Not when Federer won three Grand Slams after the age of 35, Nadal and then Djokovic became the oldest year-end No 1s, and no Major winner is under the age of 30.

But in Zverev, men’s tennis has the strongest candidate for succession.

Also read: Sascha Zverev has a Grand Slam problem but, luckily for him, he has age on his side

One year ago, Zverev made his debut at the ATP Finals as and fell in the group stages after a poor run, so poor that he himself said that he would not even have been top 50 if he played the rest of the year as he had played in the last few tournaments.

But in 2018, in a field that only has the top eight players (top 10 in this case as Nadal and Juan Martin del Potro pulled out with injuries), he came out on a top with keeping his head as strong as his game – the biggest factor in his win.

Overcoming the Djokovic wall

Zverev is a solid player with a strong game and striking weapons – a big serve and powerful strokes on both flanks. But more often than not, he has the tendency to not use them, and his presence of mind, in tough spots. Game sense, after all, comes with experience and that is what has been expected of the German.

A very good example of this was when four days ago, Zverev lost the plot and match against Djokovic in the round-robin clash. He had two break points at 4-4 in the first set – the only break points the world No 1 faced all week before the final – and lost them. After that one bad slip-up, he just couldn’t bring himself back and managed to win just one game after that in a lopsided loss. At the Shanghai Masters in October, Zverev had won just three games in another huge loss to Djokovic.

But something changed in the final, the biggest in the 21-year-old German’s career so far. He played a courageous and headstrong game. He served well, didn’t let it come under pressure against the best returner in the world and sent down powerful groundstrokes from the baseline. Using his two-handed backhand, he went toe-to-toe with Djokovic’s defensive style in long rallies and in a poignant role reversal, it was the Serbian who was finding it difficult to keep up and return.

In Zverev’s own words, he was trying to think less and be more aggressive, and as simple as it sounds, it is exactly the combination that works.

Mixed 2018 season

Unlike Djokovic, Zverev has had a mixed season. But much like Djokovic, Zverev has changed a lot of small things in his approach this season.

The German has ATP World Tour-leading 58 wins (58-19 overall) in 2018 with three titles and will finish as the world No 4 for the second straight season. In 2017, he had 55 wins and five titles but by the time he ended the season, he was drained.

He started this year with poor form as well, going down to Hyeon Chung in a strange, five-setter at the Australian Open followed by early losses till Indian Wells before a runner-up finish in Miami.

In fact, Zverev has lost early to the most unlikely opponents this year: Andreas Seppi, João Sousa, Robin Hasse, Malek Jaziri, Marius Copil, with the toughest ones being Philipp Kohlschreiber (US Open) and Ernests Gulbis (Wimbledon.)

And while he has won three Masters titles, the only active player apart from the Big Four to hold this distinction, he has never gone past the quarters at a Grand Slam – his best finish was stumbling into the quarter-final at the French Open this year.

Even with a triumphant finish to the season, fact remains that Zverev is not close to a finished product.

But the German recognizes this inconsistency and it working on it. He hired Ivan Lendl as his coach before the US Open, the man who helped Andy Murray cross the barrier from talented player to Grand Slam champion. And the difference showed in the final, days after his implosion.

Lendl, Alex Zverev Sr (his father and coach), Federer, Djokovic and half the tennis world all know it and have said it often: Sascha has what it takes to win against anybody. And maybe the win in London will finally help him internalise this as well.

If he can play the way he did against Djokovic, there is a good chance that Alexander Zverev can finally give men’s tennis a top player who is not 30. And that alone makes the 2019 season well worth the wait.