On Sept. 7, Spain's Carlos Alcaraz, the youngest men's singles player in the Open Era to reach the US Open quarterfinals [1], retired from his match against Canadian Felix Auger-Aliassime after the fourth game of the second set [2] due to injury. According to USA Today, the 18-year-old was having issues with his right adductor [3]. "It's really tough to end a great tournament like this, but I had no choice to still play," he said after the fact. "I have to take care of my body and to stay healthy." While some people may think that Auger-Aliassime won by walkover, advancing due to a retirement is different, technically speaking. Here, we break that down.

What Is the Difference Between a Walkover and Retiring a Match?

According to Friend at Court, a book of rules and regulations from the United States Tennis Association (USTA) [4], a retirement occurs when a player cannot continue a match due to injury or illness. It can also occur due to "personal circumstance or adult discipline." A walkover can still occur due to a player's injury, but it is initiated before a match, not during. For instance, last fall, Williams withdrew from the 2020 French Open because of a left Achilles injury [5] that she sustained at the US Open weeks prior. This caused her would-be opponent, Bulgarian Tsvetana Pironkova, to advance by walkover.

However, on June 29 of this year, Serena Williams retired mid-match during the first round of 2021 Wimbledon because of a hamstring injury [6], marking the second time Williams had to retire from a match at a major [7], ESPN reported. Aliaksandra Sasnovich of Belarus advanced due to this retirement, not via walkover. The same thing applies to Alcaraz's case: Auger-Aliassime advanced through to the 2021 US Open semifinals because of Alcaraz's retirement. A walkover doesn't apply.

What Is the Difference Between a Walkover and a Default?

The main difference between a walkover and a default lies in who initiates the action. A player is the one to initiate a walkover when they withdraw from a match beforehand because of injury, illness, or personal circumstance. "Refusal to play for any other reason is treated as a default," the rules state. A default happens when an official decides the player cannot take part in or continue a match due to violation. "Examples of this kind of default include a player who does not show up, a player who is defaulted for lateness, and a player who is defaulted for receiving an injection, infusion, or supplemental oxygen," the rules state.

For instance, 20-time Grand Slam singles title winner Novak Djokovic was defaulted from his fourth-round US Open match last year and, subsequently, the entire tournament for hitting the line judge with a ball [8]. His opponent, Pablo Carreño Busta, advanced to the next round, and the USTA said at the time that Djokovic would lose all ranking points earned at the US Open [9] and be fined the prize money [10] won at the tournament, plus any of the fines from the incident itself.

Does a Walkover Count as a Loss?

Though the phrase "won by walkover" is used — for example, Naomi Osaka withdrew from the Western & Southern Open final [11] in August 2020 because of a hamstring injury, and Belarus's Victoria Azarenka was crowned champion by walkover [12] — a WTA spokesperson told POPSUGAR that a walkover does not count as a match win or a match loss for either player, meaning it does not affect their win-loss record. (A spokesperson working for the French Open further confirmed that Williams's tournament withdrawal, and subsequent walkover, at last year's French Open was not considered a defeat.)

Retirements, though, do count as a match win or loss for the players. Williams's retirement from 2021 Wimbledon therefore counted as a match loss for her, the WTA spokesperson confirmed, as would Alcaraz's retirement from the 2021 US Open, and therefore impacts ranking.