Novak Djokovic waited five years to return to Indian Wells but the Serb's campaign in the California desert came to a close much quicker than anyone expected after 20-year-old Luca Nardi pulled off a stunning 6-4, 3-6, 6-3 upset.

The world number one had not competed at the tournament since 2019 due to US travel restrictions related to the COVID-19 pandemic and saw his hopes of winning a record sixth title dashed by the 123rd ranked lucky loser.

"He really didn't have anything to lose, so he played great. Deserved to win," Djokovic told reporters.

"I was more surprised with my level. My level was really, really bad.

While Djokovic was uncharacteristically sloppy, Nardi was sharp, racing around the court and pounding serves and forehands to beat the 24-time Grand Slam champion he grew up idolising.

"I made some really terrible unforced errors," Djokovic said.

"Just quite defensive tennis and not much on the ball in the third, and that's it. He just stepped in and he used the time that he had.

"He was playing more free and more aggressive than I did, and going for his shots and that break on 3-2 in the third was enough."

"This is a miracle," Nardi said in an interview after the match on the Tennis Channel.

Setting the tone early with his hard-hitting shots, Nardi frustrated Djokovic all evening.

There was a moment when Nardi was surprised by an "in" call and casually hit the ball back over the net.

It resulted in a winner and led to Djokovic complaining to the official about a potential hindrance.

"He reacted to the call, he didn't make the call, he didn't actually stop the point," the umpire replied. "Just because he stops, doesn't mean the point stops."

Djokovic was not happy with this interpretation.

"He literally stopped and that completely confused me. And I stopped as well. How can you not make that judgement?" the 24-time major title winner said.

The umpire emphasised that just because Nardi stopped did not make it a hindrance.

The ATP rulebook differentiates between inadvertent and deliberate hindrance, where "deliberate is defined as the player meant to do what it was that caused the hindrance or distraction." 

Nardi got into the field as a "lucky loser," which is a player who stumbled on the final hurdle in qualifying but made it into the main draw as a replacement for an injured player who pulled out before the first round.

In Nardi's case, he stepped in for number 30 Tomas Martin Etcheverry and received a bye through the opening round.

He went on to become the lowest-ranked player to beat Djokovic in a Grand Slam or ATP Masters 1000 level event, surpassing number 122 Kevin Anderson in 2008 in Miami.