Roger Federer was already a long way clear at the top of the list of men with the most wins in Grand Slam singles matches, so becoming the first to 300 wasn't a major distraction.
He reached the milestone at Rod Laver Arena on Friday, when he moved into the fourth round of the Australian Open with a 6-4, 3-6, 6-1, 6-4 victory over Grigor Dimitrov.
''It's very exciting, I must tell you,'' Federer said of his latest record, adding that reaching 1,000 wins in tour matches last year was also a cause for celebration. ''It was a big deal for me.
''Not something I ever aimed for or looked for, but when it happens, it's very special. Yeah, you look deeper into it, I guess, where it's all happened and how. So it's very nice.''
Federer now is 67 clear of No. 2 Jimmy Connors in Grand Slam singles wins. His aim now is for an 18th major title - he hasn't added to his collection since winning Wimbledon in 2012. He got close last year, losing the finals at Wimbledon and the U.S. Open to No. 1-ranked Novak Djokovic.
The 34-year-old Federer improved to 5-0 against Dimitrov, a young Bulgarian with a similar style, including two wins in two weeks. Dimitrov took a set off Federer for the first time in the quarterfinals at the Brisbane International, and did that again in Melbourne.
Dimitrov needed treatment at times, but Federer didn't cut him any slack - he lost in the third round here last year, his worst run at Melbourne Park since 2001.
''You're aware of it - I'm a veteran so I,'' don't get distracted, Federer said. ''I've been fooled too many times when I was a teenager. I hope he's OK.''
Defending and six-time champion Serena Williams taught a teenager a few lessons in the following match on center court, racing to a 6-1, 6-1 win in 45 minutes over 18-year-old Russian Daria Kasatkina.
Williams next plays Margarita Gasparyan, who beat Yulia Putintseva 6-3, 6-4.
Earlier on Rod Laver, 2008 champion Maria Sharapova collected her 600th win at tour level.
Sharapova, a four-time finalist, advanced with a 6-1, 6-7 (5), 6-0 win over Lauren Davis before she was reminded of the milestone.
''Wow. I've won 600 matches?'' Sharapova asked, responding to a question in an on-court interview. ''Is this like a friendly reminder that I'm getting old?''
''I think it's a proud number,'' she said later.
The fifth-seeded Sharapova will next play No. 12 Belinda Bencic, who won the opening match on Rod Laver Arena 4-6, 6-2, 6-4 against Kateryna Bondarenko.
Roberta Vinci, who ended Williams' bid for a calendar-year Grand Slam in 2015 with a shocking semifinal win at the U.S. Open, lost 0-6, 6-4, 6-4 to Anna-Lena Friedsam.
Kei Nishikori had some trouble with his wrist, taking a medical timeout and losing the next set before recovering to reach the fourth round at the Australian Open with a 7-5, 2-6, 6-3, 6-4 win Friday over No. 26-seeded Guillermo Garcia-Lopez. He'll next play 2008 Australian Open finalist Jo-Wilfried Tsonga, who beat fellow Frenchman Pierre-Hugues Herbert 6-4, 7-6 (7), 7-6 (4).
Nishikori reached the 2014 U.S. Open final and the quarterfinals at the Australian and French Opens in 2015 before withdrawing from his second-round match at Wimbledon with an injured left leg.
Returning to the fourth round at Melbourne Park for the fourth straight year was a confidence booster, and he said the right wrist ''actually, it was OK.''
''In the first set I was sore but after treatment I felt better,'' he said. ''I tried to stay tough, concentrated again - I played better in last set.''
There was a full house on Margaret Court Arena for the match, including a big section of Japanese supporters waving flags, while matches on uncovered outside courts were delayed because of rain. Play finally began on some outdoor courts after more than a six-hour delay, and seven doubles matches were postponed.
No. 15 David Goffin beat No. 19 Dominic Thiem 6-1, 3-6, 7-6 (2), 7-5 - his first win against a top-20 player at a Grand Slam. He faces a tougher proposition next: Federer.