MELBOURNE -- The match was only four minutes old when Mother Nature interrupted.
History suggested this would be a decisive advantage for the Swiss, who entered the encounter with 264 indoor wins -- 224 more than his opponent.
Although not a clean match by any standards, Federer handed Dimitrov a 6-4, 3-6, 6-1, 6-4 loss Friday and reached the fourth round of the Australian Open.
Federer misfired throughout, ending the match with 55 unforced errors. But he was able to break his Bulgarian opponent four times to secure the win.
At 34 years, 176 days, Federer is the oldest man to reach the round of 16 here since Andre Agassi 11 years ago.
After winning a 48-minute routine opening set, Federer began to unravel. In the second, Dimitrov broke Federer for only the third time in five career matches to take the early lead. Down 3-1, Federer had two chances to get back on serve, but Dimitrov unloaded a couple of thunderous forehands that eluded Federer to consolidate the break.
In the final two frames, Federer lost only five games, giving him his 300th career Grand Slam match win, 67 more than second-place Jimmy Connors.
"It's very exciting, I must tell you," Federer said of reaching the milestone. "It was a big deal for me. Not something I ever aimed for or looked for, but when it happens, it's very special."
Federer already has advanced further in Australia than he did a year ago when he fell to Andreas Seppi in the third round -- the first time he failed to reach the semis since 2003.
"It was a difficult situation to be in," Federer said of his performance in the second set. "Grigor was playing well, and I was struggling. Maybe I was tired a little, just didn't feel like it was happening.
"It was important to get the early break in third, and everything started to come back."
And now Federer rolls into the second week, where No. 15 seed David Goffin awaits. The Belgian earned a hard-fought 6-1, 3-6, 7-6 (2), 7-5 victory against Dominic Thiem in a match that lasted two minutes shy of three hours.
Goffin fended off a hefty 55 winners from his opponent to secure the victory.
Federer is 3-0 in his career against the Belgian but did drop a set against him at the Basel Indoors late last season.
"So I just have to be focused on what I have to do, like every match, to be aggressive and take every opportunities as I can," Goffin said of his upcoming encounter. "At the end we will see. But for the moment, I'm just enjoying my performance today and take a day off tomorrow and be ready for the next round."
A year ago, Nishikori reached the Aussie Open quarterfinals for the second time, but to get back there, he'll need to stop No. 9 Jo-Wilfried Tsonga, a 6-4, 7-6 (7), 7-6 (4) winner over French countryman (and qualifier) Pierre-Hugues Herbert.