The Australian Open suffered an upset body blow on Thursday as second seed Casper Ruud was routed 6-3, 7-5, 6-7 (4), 6-2 by unfancied American Jenson Brooksby.

The second-round shocker left Stefanos Tsitsipas on third as the top remaining seed after holder and tournament No. 1 Rafael Nadal was knocked out on Wednesday by Mackenzie McDonald of the US.

Ruud saved three match points in the third set to stretch out the encounter; but Brooksby, ranked 65t,, finally prevailed on his fifth as he won the fourth set to wrap up business.

Casper Ruuid crashed out in the second round. Photo: Roger Parker International Sports Fotos Ltd

Ruud was already plotting strategy with his team after the shock to the system for a two-time Grand Slam finalist who missed playing here a year ago due to an ankle injury in the run-up period.

“I ended up getting broken a bit too many times (nine),” the Norwegian said. “That’s was maybe the key to part of the reason why I lost today.

“I didn’t serve precisely enough; Jensonis gonna make it tough for you if you don’t serve well.”

The American outsider was able to put aside his failure to close out a straight-sets result, taking another hour and a quarter to finally post the upset win.

“Sometimes in these three out of five situations you can get a little more tired mentally and physically for sure,” the winner said.

“I was getting a little more frustrated that I didn’t close it out, and my mentality was changing a little bit.

“The biggest question is how do you respond… I just told myself to reset, keep doing what I was doing in the start of the fourth, and just not let the end of the third just change how I play going forward.”

Jenson Brooksby beats Casper Ruud in his second round match. Photo: Roger Parker International Sports Fotos Ltd

Ruud will carry on with his plan to use much of February as a training month after filling part of the off-season with an xhibition tour of South America with Nadal.

“I look forward to having some time off, spending it at home, getting ready for hopefully another good and long year on tour when I start again,” he said.

The Scandinavian added that he and his team – coached by his father, a former ATP player – will consider how to better utilise the brief tennis off season in future.

“We will consider what we will do in December this year, and (what is) the right way to prepare for the Australian Open..

“There are many factors that come into play. I’ve done what I felt was the right preparation but wasn’t able to perform and win as many matches as I hoped here this year.”

Emiul Ruusvuori lost to Andrey Rublev in Melbourne on Thursday. Photo: Roger Parker International Sports Fotos Ltd

Fifth-seeded Andrey Rublev spanked Finland’s Emil Ruusuvuori 6-2, 6-4, 6-7 (2), 6-3 as the six-time Grand Slam quarter-finalist reached the third round.

He will now play Brit Dan Evans, a 6-4, 6-4, 6-1 winner over France’s Jeremy Chardy.

“It was a good day, the conditions were pretty tough,” Evans said. “I’m so happy to get out in three straight sets. It was a pretty solid performance.”