They both struggle to win matches on grass. Such a jibe, utterly unthinkable when the Mallorcan was stylishly winning this title in 2008 and 2010, are all the rage at this year's Wimbledon.
While Vicente del Bosque's all-conquering Spaniards have crashed and burned at the World Cup in Brazil, Nadal has lost his last three matches on the green stuff, a run which stretches back to July 2012.
And the statistic doesn't look any better when you consider that his three victorious opponents - Lukasz Rosol in the second round at Wimbledon in 2012, Belgium's Steve Darcis in the first round here last year, and Dustin Brown at Halle a fortnight ago - were all ranked outwith the world's top 80 players.
Spanish supporters, however, shouldn't despair just yet. While Nadal waxed philosophically about the high-profile failure of his countrymen, in personal terms he regards this year's Wimbledon as a whole new ball game.
While this tournament remains the "most dangerous" major tourna-ment on the calendar - at least until next year, when the grass-court season gains an extra week - a combination of some post-Halle downtime on the beach in Mallorca and the condition of his knee, which is permitting him to train even harder than ever before, has given him new confidence.
After a record ninth Roland Garros win, an outright victory for the World No 1 would take him clear second on the all-time list with 15 major wins, just two behind Roger Federer.
"Everybody in Spain is sad about what happened in the World Cup," Nadal said. "But I am not more motivated because Spain lost in the World Cup. It's normal that this can happen.
"Everybody who understands about sport understands that there is a beginning, and an end of things. Wimbledon really is the most dangerous tournament of the year," he added. "When I arrive at Roland Garros I have already played for one month on clay, a lot of matches.
"So more or less I can imagine how I am going to play. The US Open is the same. And Australia, it is true that it is at the beginning of the season, but it is a surface we know so it is not a dramatic change.
"But I am feeling better this year than the last couple of years, seriously. I am able to move myself more freely now, I'm not scared about my knee. It is true that for the last couple of years I didn't play lot of matches on grass.
"But I am confident I can do it again. I am not talking about winning, but I am talking about playing better than I did the last couple of years on grass."
If that is the good news, the bad news is that Nadal is located in an awkward portion of the draw. Martin Klizan of Slovakia is tricky first off the bat, while the likes of Richard Gasquet and Milos Raonic are also difficult potential opponents.
"Seriously, in every tournament of the year, even on clay, probably some of you think that Rafa, when the tournament starts, analyses Djokovic, Federer, the other ones," said Nadal.
"I start from the first round in every surface. And as you can imagine even more here on grass."
While Nadal was feeling pain-free after recent issues with his knee and back, Novak Djokovic's injury scare related to his wrist.
Having originally sustained the problem in Monte Carlo in April, the Serb managed it through Roland Garros but pulled out of his grass-court warm-up event at Stoke Park for fear of aggravating the problem further.
"Right now I don't feel any pain," said the Serb. "But when I'm changing surfaces, especially from clay to grass, in the opening few days of the practice here I got a little bit of a strange sensation in the wrist. Now it is fine, hopefully it can stay that way."
While Nadal struggles to win matches on grass, Djokovic these days struggles to win finals on any surface. He has lost five out of the last six, including two to Andy Murray.
"Roland Garros in general has taken a lot out of me emotionally," said Djokovic. "I needed four or five days rest to try to get my mind off tennis. That's what I got, so now I'm very motivated to play Wimbledon."