Djokovic routed nine-time Roland Garros winner Nadal in straight sets in a brutal quarter-final demolition on Wednesday that condemned the Spaniard to only his second loss in 72 matches in Paris since his 2005 debut.
"At the end of the day, he's human and it's normal to have seasons like this," said world number one Djokovic.
And it has been a poor season by Nadal's lofty standards.
It was always likely to be a struggle after he underwent surgery on his appendix in November last year, which in turn followed a three-month absence to rest a wrist problem.
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From his second round exit at Wimbledon, the 14-time Grand Slam title winner played just three more tournaments in 2014, missing the defence of his US Open title in the process.
"It's normal to have people questioning his game now. But if you need a reminder of who he is, just look at his career stats and Grand Slams that he has won," said Djokovic.
Nadal, who will likely slip out of the world top 10 next week for the first time since April 2005, is no stranger to rebuilding his often injury-scarred career.
After losing in the second round at Wimbledon in 2012, he didn't play again for eight months due to knee tendinitis.
His powers of recovery stunned his critics as he raced through 2013, winning another French Open and the US Open, just two of 10 titles he collected that season which ended with a 75-7 win/loss record.