Rafael Nadal is the “ultimate” favorite to win the 2018 US Open in the men’s singles draw, according to 1989 champion Boris Becker.

The Spaniard progressed to the quarterfinals Sunday with a four set win over Nikoloz Basilashvili and will now face Dominic Thiem in the last eight. The defending champion is one of the pre-tournament favorites.

Becker points to Nadal’s phenomenal 2018 season, which has seen him win five titles thus far which includes the French Open and three Masters Series titles in Monte Carlo, Rome and most recently in Canada.

The Rogers Cup in Toronto was the first Masters Series title on hard courts for Nadal since 2013, which Becker believes puts him in good stead to win the title at Flushing Meadows. The world number one, however, is going to have to beat an in-form Novak Djokovic with the Serb picked as the number two favorite by Becker.

Djokovic has finally found his best form after struggling at the start of the year. He won Wimbledon in July and then followed it up with a title at the Cincinnati Masters in August, making him one of the favorites for the title in New York.

Rafael Nadal
Rafael Nadal (L) and Novak Djokovic's last meeting was in the semi-finals at Wimbledon 2018 when the latter won. In this picture, Nadal (L) and Serbia's Djokovic smile during an exhibition game during 'Kids Day' on The Philippe Chatrier Court in Paris on May 26, 2018, on the eve of The Roland Garros 2018 French Open tennis tournament. CHRISTOPHE SIMON/AFP/Getty Images

The Serb, seeded number six, looks in imperious form coming into the latter stages of the tournament having come through in straight sets against Joao Sousa to make the quarter-finals. Becker’s third pick for the title at Flushing Meadows was Roger Federer, but that now is inconsequential after the Swiss ace suffered a shock loss to Australian John Millman on Monday night.

The 20-time men’s singles Grand Slam champion was expected to make his way past the Australian and face Djokovic in the last eight, but the Serb will now be favorite to make the semifinal when he takes on Millman.

"For me Nadal is the ultimate favorite, because his season was unbelievable and he is the number one,” Becker said, as quoted on Tennis World USA. "[Nadal] won in Toronto a little time ago and he is going through a great time. ... After that I would say Djokovic - he won Wimbledon and this is big. Then Federer, who is loved by New York fans, but we will have to see how he handles such a long tournament.”

Becker, a former world one, also picked two players not on the list of pre-tournament favorites — the first Alexander Zverev, 21, and a three time Masters Series champion and second Juan Martin del Potro.

The former is already out of the tournament having lost in four sets to Germany’s Philipp Kohlschreiber, while the latter is in the quarterfinals and will face John Isner on Tuesday.

Del Potro can certainly be counted as a contender for the title as he won the tournament in 2009, beating Nadal and Federer on the way to the title.

"I would also mention [Alexander] Zverev and [Juan Martin] del Potro, because this last one knows how to win here,” Becker said.