Four-time Grand Slam winner Naomi Osaka says it was "a little difficult" to be eliminated in the second round of the 2024 U.S. Open.

"It's been a little difficult because obviously I can only gauge how I'm doing by results," Osaka said, per ESPN. "Like, I feel faster. I feel better, but I lost in the second round. ... Yeah, it's a little rough because I do take these losses really personally.

"It's like a dramatic word, but I feel like my heart dies every time I lose. It sucks a lot, but I've been trying to be more mature and learn and talk more about them."

The two-time U.S. Open champion lost 6-3, 7-6 (5) to Karolina Muchova in her return to the event for the first time since 2022.

After a strong start, Osaka dropped five straight games to Muchova to concede the first set before losing the tiebreaker in the second.

"I think during the pressure moments I got nervous, and I don't know if I just have to keep playing more matches and get used to that feeling, especially on a really big stage," Osaka said, per ESPN.

She added: "Honestly, if I get past the disappointment, I feel pretty proud of myself to have gotten that many opportunities while still feeling like I could have played much better."

Osaka made her return to the court in January after almost a year and a half away from the game, taken to focus on her mental health and give birth to her daughter last July.

Recent tournament results include a first-round elimination from the 2024 Paris Olympics in July and a qualifying-round loss at the Cincinnati Masters earlier this month.

Osaka said on Instagram after her elimination in Cincinnati that she felt disconnected from her body in a way she compared to "being postpartum."

She came back to celebrate a strong opening to the U.S. Open after defeating No. 10 Jelena Ostapenko 6-3, 6-2 to mark her first win over a top-10 player in four years.

Osaka will now hope to build on that first-round victory as she looks to return to the dominant form that saw her win the U.S. Open in 2018 and 2020.