MELBOURNE - Casper Ruud defended his decision to play exhibition matches against Rafa Nadal in South America ahead of the Australian Open but said it may not have been the ideal preparation after the top two seeds crashed out following second-round defeats.

A day after an injured Nadal saw his title defence end with a 6-4 6-4 7-5 loss to Mackenzie McDonald, second seed Ruud fell 6-3 7-5 6-7(4) 6-2 against another American in Jenson Brooksby on Thursday to leave the men's draw at Melbourne Park depleted.

Ruud played Nadal in Buenos Aires, Belo Horizonte, Quito, Bogota and Mexico City over two weeks in December and competed in two matches at the season-opening United Cup mixed team tournament before losing to Laslo Djere in Auckland.

"It's very easy to sit here now and say that was bad for maybe both Rafa and I due to the fact that we lost early here," Ruud told reporters.

"At the same time, I see no reason why we couldn't have a good Australian Open or made better results down here. I think it's coincidental sometimes.

"I've realised there are, in my eyes, so many players these days that you'll have a chance to beat many players on tour, and there's a chance you will lose to many players on tour."

The 2022 French and U.S. Open runner-up admitted he could rethink his schedule at the end of this year.

"It was maybe not enough to be able to perform well here this year," Ruud said.

"So it will be considered by me and my team what we will do in December this year, and if this was the right way to prepare for the Australian Open or not, who knows?

"Maybe it looks like it was not right way, but there are many factors that come into play. I have 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."

(Reporting by Shrivathsa Sridhar in Melbourne; Editing by Kim Coghill)