His first-round loss to Fernando Verdasco unearths questions that appeared buried late last year. Chief among these is whether Nadal will ever contend for a Grand Slam again.
Verdasco defeated Nadal 7-6 (6), 4-6, 3-6, 7-6 (4), 6-2 in a thrilling match on Rod Laver Arena. A former top 10 player, Verdasco is no slouch. He could even give Novak Djokovic fits in a first-round clash. Instead of Verdasco's magnificent performance, though, it was the way Nadal withered in the final set that spoke volumes about the once-dominant player.
Nadal looked limited. His grunts sounded like vintage Nadal. His movement along the baseline seemed like vintage Nadal. But his weapons have diminished. He was giving all he had. It's just no longer enough.
It's only the second time in Nadal's career that he has lost in the first round of a Grand Slam. It comes on the heels of his going Slam-less in 2015.
The loss also marks two consecutive Grand Slams in which a player came back to polish off Nadal. Last year, it was Fabio Fognini in the third round of the U.S. Open. This year, unseeded Verdasco.
Whether Nadal's late-match collapse was due to physical, mental or tactical limitation, it's obvious he is no longer a given to reach the latest rounds at Grand Slams.
Over the past year, his status in the "Big Four" has been suspect, given that he's been ranked outside of the top four for so long.
In his post-match press conference Nadal told reporters (via the Australian Open website): "I know I did everything that I can to be ready for it. Was not my day. Let's keep going. That's the only thing. No, no, there is no more things to do than keep practicing hard, keep practicing the same way that I was doing the last four, five months."
No, Nadal, you can't keep just doing what you've been doing. It's not working, at least not well enough to win a Grand Slam.
Although his struggles get more attention at Grand Slams, Nadal's performances are on the decline in general. Along with not winning a Slam, last year Nadal won just three ATP World Tour titles. That was the fewest he'd won since 2011. The only time Nadal won fewer than three tournaments was in 2004.
Last year, Nadal even had issues on clay. He's won 47 of his 67 career singles titles on clay. However, in 2015 he didn't win any Masters-level French Open tuneups. In fact, Nadal failed to capture a title in five consecutive clay-court tournaments.
Nadal last won a Grand Slam at the 2014 French Open. That was a difficult battle against Djokovic who was just beginning to dominate the ATP Tour. Winning at Roland Garros had become a given for Nadal. But so had winning in general for Djokovic.
That's why when Djokovic upended Nadal in the quarterfinals of the 2015 French Open, the narrative was more about the Serbian elevating his game than it was about the Spaniard's decline.
Then Fognini happened. Speculation returned. "What's wrong with Rafa?"
Experts blamed everything from his lack of confidence to his badly beaten up knees and, of course, Uncle Toni Nadal.
Perhaps it was time for Nadal to bring in a "super coach" like Andy Murray did with Ivan Lendl and Djokovic with Boris Becker.
In October 2015, when asked by AFP writer Talek Harris about the possibility of bringing in a super coach, Toni Nadal left it up to Rafa.
"We have a group and I'm the coach of Rafael forever, since Rafael was three years old...and things were always good for us," Toni said. He added: "Maybe if next year Rafael is playing not too good, then I think he can think about some changes in his game or in his team."
Although a new set of eyes might help, Nadal's problems go beyond coaching. The 14-time Grand Slam champion is declining. The once-formidable forehand failed him against Verdasco. That used to be Nadal's kill shot.
Nadal told reporters: "I was competitive. [But] in terms of creating damage to the opponent with my forehand, I didn't. So I was hitting forehands, and he was able to keep hitting winners—to keep going for big shots in a not-very-bad position."
Verdasco jumped on Nadal's groundstrokes like they were sitting on a tee. In his post-match interview with Jim Courier, Verdasco commented that he noticed the drop-off in Nadal's game.
"He started playing a little less deep and strong, so I started coming in, inside the court, trying to be aggressive, and it went well," Verdasco said.
Would a new team solve that problem? Perhaps Uncle Toni has run out of ideas. His declaration that his game plan has been working since Nadal was three years old epitomizes complacency.
Serena Williams won 13 Grand Slam titles in nearly 13 years on the WTA Tour with her mother and father at the helm. After she suffered a shocking first-round loss at the 2012 French Open, Williams brought on Patrick Mouratoglou as coach. Under Mouratoglou, Williams has won eight Grand Slams in four years.
Tweaking his team may be too little, too late for Nadal. His body simply may be unable to deliver. The same dogged style that propelled Nadal to the top may have done him in.
A few years ago, when Nadal was tearing through the tour, the talk centered on his topping Federer's 17 Grand Slams.
Now you have to wonder if Nadal might retire before Federer. Unreal? It's no more mind-boggling than Nadal's swift decline. It's also why you have to ask whether Nadal will ever contend for another Grand Slam.
As long as the French Open is played on clay, he stands a chance. But even that is no longer a given.