Roger Federer says fellow tennis great Serena Williams "went too far" in her outburst at the umpire during September's US Open final.
Williams received a code violation for coaching, a penalty point for racquet abuse and a game penalty for calling the umpire a "liar" and a "thief" during her defeat by Naomi Osaka.
Federer said the incident could have been handled differently.
"I feel like Serena should have walked away," he told the Sunday Times.
"She did, but she went too far. She should have walked earlier."
Federer did, however, say Williams' actions were "a little bit excusable".