'S-HERTOGENBOSCH, Netherlands -- Former No.1 Naomi Osaka kicked off her grass-court season with a win at the Libema Open, defeating No.32 Elise Mertens 6-2, 6-4 in the first round on Tuesday. The win is Osaka's first on grass since 2019 Birmingham. 

's-Hertogenbosch: Draws | Schedule | Scores

"I'm kind of taking it as if this is my first year on grass," Osaka told reporters after the win. "I think even now, this is my first time at this tournament so in some ways I feel like a newbie all over again.

"I've been in Europe since April, so this is a lot of commitment for me. I'm really happy that I'm doing this."

Osaka's strong serving and crisp baseline hitting was on full display in the 70-minute victory. The match was Osaka's first since her memorable performance in the second round of Roland Garros, where she held match point on eventual champion Iga Swiatek.

"I play better in the big stages against the best players," Osaka said when asked to reflect on that Swiatek match. "I think I've always been that way.

"It's more that I need to keep that level in smaller events."

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Now begins the transition to grass, a surface that Osaka should excel on. Tuesday's match was just her 23rd career match on the surface. She has yet to progress past the third round at Wimbledon, but she has made a pair of grass-court semifinals. The first came as a teenager at an ITF 50K in 2015, where she beat Anett Kontaveit to make the final. The second came on the Hologic WTA Tour at 2018 Nottingham. She lost to Ashleigh Barty. 

Osaka improved her head-to-head record over Mertens to 4-2 with an unbreakable serving performance. After saving break point in her second service game, Osaka did not face a break point for the remainder of the match, winning 90 percent of her first-serve points. She was also perfect on her own break-point chances, breaking Mertens three times. 

"Definitely really happy with my serve," Osaka said. "I felt probably more confident in it on this surface than any other surface, so I'm glad I was able to pick that up quite fast.

"What do I need to improve? Probably being more confident on my returns. I felt I got a little hesitant and kind of reverted back to clay court. I thought about pushing back my returns at a certain point. But I know I have to commit."

Osaka finished the match with 21 winners to 13 unforced errors, while holding Mertens to just nine winners. The victory avenged Osaka's loss to Mertens in the third round of the BNP Paribas Open in March. 

"I felt initially on clay, coming back this year, more comfortable than my first day on grass," Osaka said. "But I'm being told that I'm playing pretty well in practice. I think I just need a lot more days on it and I need to believe in myself a lot more.

"Hopefully if I win a lot more matches during these preparation tournaments then I'll believe in myself. That's the key."

Osaka will face Dutch wild card Suzan Lamens in the second round. Ranked No.140, Lamens defeated Bernarda Pera 4-6, 6-2, 6-4 in the first round.