Fresh after achieving the 'Undecima' at Monte Carlo and Barcelona, Nadal failed to defend his title at the Mutua Madrid Open, when he lost in straight sets to Dominic Thiem in the quarterfinals, ending his 21-match and record 50-set winning streaks on clay.

Novak Djokovic started off with a fourth round loss at the Australian Open, losing to Chung Hyeon from South Korea in three close sets.

At the Italian Open, Djokovic was able to reach his first semifinal of the year, losing to eventual champion Rafael Nadal in straight sets.

After a triumphant grass season, Djokovic started his US Open Series with a third round showing at the Rogers Cup, losing against eventual runner-up Stefanos Tsitsipas.

Here he faced Roger Federer in the final and defeated him to win his first Cincinnati Masters title convincingly in straight sets.

At the grass season, Federer claimed his third title of the year at the MercedesCup defeating Milos Raonic in the final in straight sets.

He came into the Swiss Indoors as the defending champion, he defeated qualifier Marius Copil in the final to claim his fourth title of the year.

Juan Martín del Potro started the season at the ASB Classic reaching the final, where he lost to Roberto Bautista Agut in three sets.

He then went to win his first Masters event title at the BNP Paribas Open defeating defending champion and world No.1 Roger Federer in the final.

Del Potro entered the China Open, where he faced unseeded Nikoloz Basilashvili in the final, but ended up losing in straight sets.

He returned to action at the Abierto Mexicano Telcel, where he reached the semifinals, before losing to eventual champion Juan Martín del Potro in straight sets.

He then bounced back at the New York Open claiming his fourth career title defeating local favourite Sam Querrey.

At the Wimbledon Championships, he reached his second career slam final after marathon wins over Roger Federer in the quarterfinals 13–11 in the fifth and the longest semifinal match in history when he defeated John Isner 26–24 in the fifth set.

In the Asian swing, he reached back-to-back quarterfinals at the Japan Open and Shanghai Rolex Masters, losing to Richard Gasquet and Djokovic, respectively.

At the French Open, Čilić reached the quarterfinals for the second year in a row losing to Argentinian Juan Martín del Potro.

At the grass court season, he started perfectly when he claimed his first title of the year at the Queen's Club Championships defeating Novak Djokovic in the final, where he saved a match point in the second set.

Heading back to the American hardcourts, he did pretty well when he lost to eventual champions Nadal and Djokovic at the quarterfinals of the Rogers Cup and semifinals of the Western & Southern Open, respectively.

Dominic Thiem began the year at the Qatar ExxonMobil Open, where he reached the semifinals but had to withdraw prior to his match against Gaël Monfils due to an illness.

He then competed at the Rio Open and the Abierto Mexicano Telcel but lost to Fernando Verdasco and Juan Martín del Potro respectively.

At the clay season, he began with back-to-back finals at the Monte Carlo Masters and Barcelona Open losing to Rafael Nadal and Stefanos Tsitsipas, respectively.

At the Mutua Madrid Open, he upset Nadal in the quarterfinals and eventually reached the finals for the second year in a row but yet again lost, this time to Alexander Zverev.

Nishikori went on to win his sixth ATP Challenger career titles at the RBC Tennis Championships, by defeating Mackenzie McDonald in the final.

Entering Wimbledon with an arm injury, but was able to reach quarterfinals of the grass slam for the first time, where he lost to eventual champion Djokovic in four sets.

At the Shanghai Rolex Masters, Nishikori reaching the quarterfinals, he was defeated by top seed and defending champion Roger Federer.

He only picked up two wins in Davis Cup against Dušan Lajović and Delray Beach Open against Albot before losing to Peter Gojowczyk.

Their clay season was quite successful reaching the final of the Monte-Carlo Masters when they lost to American brothers M Bryan/B Bryan and winning the title at the Geneva Open defeating Dodig/Ram.

They then faced Mektić/Peya at the final of the Mutua Madrid Open but retired in the first set down a break due to Bob's hip injury, which ended his season.

On October 14, slams champions teams of Americans Mike Bryan and Jack Sock, and Frenchmen Pierre-Hugues Herbert and Nicolas Mahut gained the next two spots.

Pierre-Hugues Herbert & Nicolas Mahut began the year with a second round loss at the Australian Open to Podlipnik Castillo/Vasilevski in third set tie-break.

They won their biggest title of the year at the Mutua Madrid Open against Bryan/Bryan when Bob Bryan retired due to injury in the first set.