MELBOURNE, Australia (AP) — Rafael Nadal bowed his head during changeovers and rested his elbows on his knees, the very picture of resignation.

What already was a poor start to 2023, following a year marred by all manner of health issues, reached a low point at the Australian Open on Wednesday.

The defending champion and number one seed at Melbourne Park, Nadal injured his left hip and lost to Mackenzie McDonald 6-4, 6-4, 7-5 in the second round, abruptly ending his bid for a record-extending 23rd Grand Slam trophy.

“It’s a tough moment. It’s a tough day,” said Nadal, a 36-year-old Spaniard. “I can’t say that I am not destroyed mentally at this moment, because I would be lying.”

He pulled up awkwardly at the end of a point late in the second set against the 65th-ranked McDonald.

Nadal was visited by a trainer on the sideline, then left the court for a medical timeout. Up in the stands, his wife wiped away tears. Nadal returned to play, but was clearly compromised and not his usual indefatigable self, saying afterward that he could not hit his backhand properly and could not run much, either.

But Nadal added that, as the reigning champion of the tournament, he did not want to leave the court via a mid-match retirement.

He said the hip had been bothering him for a couple of days, but it was never as bad as it became on Wednesday. Nadal was not sure exactly what the nature of the injury was, saying that he will have medical tests to determine if it has to do with a muscle, joint or cartilage.

“‘It’s never over until it’s over’ type thing. He didn’t even want to roll over and quit. He kept fighting until basically the end, even though he maybe didn’t have all his game,” said McDonald, a 27-year-old who won NCAA championships in singles and doubles for UCLA in 2016.

“I was in the locker room,” McDonald said about the aftermath of the match, “and I was like, ‘Hey, that’s actually really big for me, because I haven’t beaten someone of that caliber.'”

This is Nadal’s earliest exit at any Grand Slam tournament since bowing out in the first round in Melbourne in 2016 against number 45 Fernando Verdasco. That also made Verdasco the lowest-ranked player to defeat Nadal in Australia — until, of course, McDonald on Wednesday.

McDonald has never been past the fourth round at a major tournament. In his lone previous matchup against Nadal, at the 2020 French Open, McDonald won a total of just four games in a lopsided loss.