On Wednesday night in Miami, Osaka dispatched Serena Williams 6-3 6-2. The difference between Halep and Williams is not only an 11 age gap but Williams is Osaka's childhood idol.
"Serena is the main reason why I started playing," she gushed. "I have seen her on TV so many times, so for me to be playing against her, I was trying to detach myself from the fact I was playing Serena and it was hard. It took me three games to adjust."
Once she did, she was soon displaying the confident hitting that had swept her to the title in the Californingn desert on 18 March.
She broke in the seventh game and held her own serve to lead 5-3. She took the Williams serve again to wrap up the set. The second set was one-way traffic and Williams's latest journey on her comeback from 13 months out to have her first child ended after 77 minutes.
The defeat was the first time Williams had lost her first match at an American hard court championship for 21 years. The pounding left her truculent enough to skip the post-match press conference.
The 36-year-old 23 time Grand Slam champion eventually released a statement. "Every tournament is an opportunity for me to better understand the areas I need to improve to be my best," it said. "Naomi played a great match and I look forward to continuing my return by progressing every day."
Osaka, who will face fourth seed Elina Svitolina in the second round, added: "I wasn't paying attention to if she was struggling or not. I would have freaked myself out if I was looking too much at her. She did hit a lot of shots which almost made me fall over and I was like: 'Wow, that's a Serena shot.'
"I was new to the tour when she left so to shake her hand at the end was pretty cool. She said: 'Good job,' but I kind of blanked out.
"It's weird playing against someone who you've grown up watching. There's a respect thing but you also want to win really bad. I just wanted her to know who I am."