Novak Djokovic, the top-ranked men's player, held serve to win his opening game against Philipp Kohlschreiber in their night match. The German owned the advantage on his serve in the second game before rain began falling. The match was later suspended for the night.
Collins struggled with her serve throughout the match, committing seven double faults and connecting on just 47 percent of her first serves.
Osaka's first-serve percentage was 66 and she won 70 percent of her first-serve points.
"In the first set I was just really flat-footed. I didn't feel like I was moving well at all,'' Osaka said. "Then I just tried to really hype myself up. My mindset was just to keep trying to get my feet moving and stay pumped up and positive.''
Osaka won her first career title at Indian Wells a year ago, propelling her to a career-best year in which she defeated Serena Williams for the US Open title. She began this year winning the Australian Open and moving to the top of the rankings. After that triumph, she fired her coach and lost in the first round in Dubai before taking on a new coach, Jermaine Jenkins.
"It is different from last year, but I think I am getting used to it,'' Osaka said. "I have been practicing on Court 3 for the past few days, and I'm really grateful there is a lot of people that come out and watch. I try to sign all of the signatures.''
Williams is seeking her 50th career WTA Tour title in the desert, where she has never won the event. And at 38, she's showing vintage form.
"I don't really play that often, so when I do, I need to play well,'' she said. "It's extra motivation for me to play just a little bit better out there.''
Serena Williams, a two-time champion at Indian Wells, retired from her match on Sunday because of a viral illness.
Ranked 36th in the world, Venus Williams endured three sets in her first two matches. She rallied past Andrea Petkovic in the opening round and followed up by outlasting No. 3 seed Petra Kvitova in a third-set tiebreaker.
Kvitova had made the finals in two of her first three tournaments this year.
Williams, who made the semifinals in the desert last year, was playing McHale for the first time. Williams rallied from early breaks down in both sets to win.
"I never played her, so it's also you're out there learning,'' Williams said.
Fifth-seeded Karolina Pliskova eased past qualifier Ysaline Bonaventure 6-3, 6-2. No. 8 Angelique Kerber outlasted qualifier Natalia Vikhlyantseva 3-6, 6-1, 6-3 and No. 9 Aryna Sabalenka defeated 24th-seeded Lesia Tsurenko 6-2, 7-5.
Playing just his third tournament of the year, Zverev said he has been sick for a week.
"That hasn't changed, unfortunately,'' he said.