MELBOURNE, Australia—The nine first-round retirements at the Australian Open—eight men and one woman—equaled a record for the most retirements or walkovers in a single round at any Grand Slam in the Open Era.

Tournament officials on Wednesday said that there were also nine retirements in the first round of the 2011 U.S. Open and the second round at Wimbledon in 2013. The U.S. Open in 2011 holds the record for most overall number of retirements with 17.

The first-round retirements at Melbourne Park included Bernard Tomic's left groin injury which forced him to quit his match with top-seeded Rafaael Nadal after losing the first set Tuesday. Among others, Tommy Haas and Alex Bogomolov Jr., had shoulder injuries and John Isner retired with a right ankle injury.