Indian Wells - World number one Serena Williams woke up after a slow start to battle past American compatriot Sloane Stephens in three sets to reach the quarter-finals in Indian Wells on Tuesday.
The 19-time Grand Slam winner defeated a dogged Stephens 6-7 (3/7), 6-2, 6-2 on center court as her emotional return from a 14-year Indian Wells boycott gathers pace.
Williams, 33, said it was good to get the experience this week of playing a two-hour match.
"I still am trying to find my bearings," she said. "I have been off a little this week.
"I just had to stay focused and use the experience of a three-set match."
Williams, who blasted 14 aces and broke Stephens six times in the two-hour, six-minute match, faces either Elina Svitolina of Ukraine or Timea Bacsinszky of Switzerland next.
The two former Fed Cup team-mates have a colorful history after Stephens, 21, upset Williams in the quarter-finals of the 2013 Australian Open in three sets.
That win ended Williams' 20-match winning streak and the two haven't been best buddies since then.
Stephens gave an interview to a US magazine a couple months later saying Williams stopped talking to her after that and Stephens now describes their relationship as just "colleagues."
Williams got her revenge later in 2013 at the US Open when she beat Stephens 6-4, 6-1 in the round of 16 and Tuesday's contest was their first since then.
Stephens' best moments came in the first set, but after that Williams was able to take charge.
The younger American came out with more energy as Williams was broken in her first two service games of the opening set. That allowed Stephens to jump out to a 3-0 lead, before Williams shook off the cobwebs.
After four service breaks in the opening six games, the two held serve to force a tiebreaker. Stephens won that on the first set point.
Williams broke Stephens in the opening game of the second, then took command midway through the set. She won the final three games, clinching the set in style with an ace.
The third set was similar to the second, as Williams broke Stephens in the first game then won the final three games to win the match.
Williams said that being number one means she can't take any opponent for granted because they step up their game against her.
"It does no good to scout players because they all play totally different against me," Williams said. "Once you accept, that you will be fine."
Williams is competing for the first time in Indian Wells since her self-imposed exile began after she won the 2001 final over Kim Clijsters 4-6, 6-4, 6-2.
Williams says she is trying to forget the events of 2001, when the 19-year-old was booed during the final. Fans accused her of rigging matches against her sister Venus and Williams countered by saying that some resorted to hurling racial slurs at her and her family members who were attending the tournament that year.