Novak Djokovic and Stan Wawrinka were set for a tantalising second round match-up at the US Open, but that will not happen after their first round exits.

Djokovic was stunned by Mariano Navone in the first round, losing to the Argentine in a gruelling five-set contest in the New York heat for his first opening round Grand Slam exit since 2006.

Wawrinka, meanwhile, saw his Grand Slam journey end as he was beaten in straight sets by Matteo Berrettini on the US Open’s Grandstand court.

The Swiss icon, who won the US Open back in 2016, is set to retire at the end of the season, so he bid farewell to the iconic New York Grand Slam.

In his final-ever US Open post-match press conference, the three-time Grand Slam champion was asked about Djokovic’s defeat to Navone in the first round.

More Novak Djokovic news

“I watched the match. It was, of course, a tough match. I think Navone is always a tough player to play, especially in those conditions and especially here. We saw it. He can really make it difficult,” said Wawrinka, before turning his attention to Djokovic’s health issues.

“Novak was struggling, we all saw, with something physically – we don’t know exactly what,” said Wawrinka about the man he’s met 27 times on the ATP Tour.

However, Wawrinka believes Djokovic still has the capabilities to challenge at the latter stages of Grand Slams.

“I think in general if you look at the year he is having in Grand Slams, he is making finals, semi-finals. But I think as long as he is playing, he knows he is going to be really dangerous,” said the Swiss icon.

Wawrinka won two of his three Grand Slam titles by defeating Djokovic in the final, although his head-to-head record against the Serbian is very one-sided.

The Swiss star beat Djokovic in the 2015 Roland Garros final, as well as the 2016 US Open final, but they were just two of the six wins he managed against the Serbian throughout his career.

With Wawrinka running out of time to play Djokovic again, his record against the 24-time Grand Slam champion currently sits at 21-6 and Djokovic’s favour.

Wawrinka’s other victories against Djokovic came at the Australian Open, the Vienna Open, as well as their very first meeting at the Umag Open in 2006.

Djokovic, meanwhile, knocked Wawrinka out of three of the four Grand Slams, with Roland Garros the only major the Swiss star went unbeaten against the tennis icon.

He also picked up victories against Wawrinka at the ATP Finals, as well as on Davis Cup duty for Serbia against Switzerland.