"The adrenaline takes over", said Raonic, the runner-up at Wimbledon in 2016.
Daniel, ranked 78, advanced to the second round after his opening opponent, Australian qualifier Thanasi Kokkinakis, retired hurt in the second set of their match on Tuesday.
Buzarnescu served for the match at 5-3 in the second set, but Williams broke at love there, then was superior in the tiebreaker that would follow.
"Hopefully", said Halep, whose No. 1 ranking is up for grabs during the Australian Open, "next round I play better".
"I (would) rather do three sets, but today he was playing well, and first match, too, the guy was playing really solid". On Rod Laver Arena, 16th seed Raonic emerged the victor against Wawrinka, a three-time Grand Slam champion who is on the comeback trail from injury. When he won in the first round, he became the oldest man to win a Grand Slam singles match since Jimmy Connors reached the second round at the U.S. Open in 1992 at the age of 40.
His signature one-handed backhand is as unsafe as ever - he had a 16-2 edge in winners on that shot Thursday - and he hit 28 aces of his own.
Wawrinka's three set points there came at 6-5, when Raonic delivered a serve at 129 miles per hour (208 kph) followed by a forehand volley victor; at 8-7, when Raonic's 125 miles per hour (201 kph) serve drew a missed return; and at 10-9, when an ace at 132 miles per hour (213 kph) did the trick. But as even as the match was in many respects - Raonic won only two more points overall, 163-161 - Wawrinka couldn't come through when he really needed to. A 123 miles per hour (198 kph) service victor gave Raonic that set.
Raonic thumped 39 aces, serving especially impeccably in the last three tiebreaks.
This is the first year the Australian Open has instituted a final-set tiebreak - up to 10 - instead of a long set.
Then, on Thursday, Karlovic lit up the scoreboard with 59 aces but also lost in a fifth-set tiebreaker, against No. 8 Kei Nishikori.
Osaka, on the other hand, cruised to her first Grand Slam win since claiming the women's singles title at September's U.S. Open.
"He nearly had it for sure", said the three-time quarterfinalist at Melbourne Park, after collapsing to his knees in relief as he was cheered on by a large Japanese contingent on Margaret Court Arena.
MELBOURNE, Australia-Kei Nishikori rallied from two sets down and won 10 consecutive games before Kamil Majchrzak retired with the score at 3-6, 6-7 (6), 6-0, 6-2, 3-0 at the Australian Open on January 15. "It's frustrating if you can't get the serve". Men staying in the hunt included 11th seed Borna Coric of Croatia and 23rd seed Pablo Carreno-Busta of Spain.