#1 Alexander Zverev

Perhaps no other young player is as highly rated as 21-year-old Alexander Zverev. It is for no mean reason that this is the case. The talented 6'6'' German came into the 2018 season ranked World Number 3 with already 2 ATP Masters 1000 titles under his belt. But progress to the second week of Grand Slam tournaments always eluded the young Zverev.
A disappointing outing at the Australian Open where he lost to Hyeon Chung in a 5-set contest in the Round of 32, meant that his failure to move to the second week of a Grand Slam continued. A disastrous first round loss to Joao Sousa at Indian Wells and it looked like Zverev was struggling. However, he was runner-up at the Miami Masters, losing to John Isner.
Cheered on by an enthusiastic German crowd, Zverev won the BMW Open at Munich beating compatriot Kohlschreiber in the final. He then won his 3rd ATP Masters 1000 title at the Madrid Open beating Dominic Thiem in the final. By then, Zverev had more ATP Masters 1000 titles than any other player currently on the Tour barring the Big 4. An impressive performance at the Rome Masters saw him lose in 3 sets to Nadal in the final.
Zverev finally broke his Grand Slam second week jinx as he made the last-8 losing to eventual runner-up Dominic Thiem. He won his third title of the year at the Citi Open beating his brother Mischa along the way. At the Rogers Cup, he lost uncharacteristically to Stefanos Tsitsipas and lashed out at his opponent after the game.
Zverev kept his best moment for the last at the Nitto ATP Finals. He became only the 4th player after Rafael Nadal, David Nalbandian and Andy Murray to beat Roger Federer and Novak Djokovic in back-to-back matches at a prestigious tournament like this. The young German tamed Djokovic in the final despite the Serb coming to the final with a near perfect set and service record.
With Ivan Lendl as his coach and the confidence that he can beat the best of the best in successive days, Zverev will surely be the favorite to break the stranglehold of the Big 4 in Grand Slams.