Four-time Grand Slam champion Naomi Osaka made a triumphant return from a two-month layoff by defeating Chinese teen Zheng Qinwen on Tuesday at the WTA San Jose hardcourt tournament.

The 24-year-old Japanese star outlasted the gritty 19-year-old 6-4, 3-6, 6-1 in a first-round match at the US Open tune-up tournament.

Osaka had not played a competitive match since losing in the first round of the French Open due to a left Achilles tendon injury.

"It's really cool to be back playing," Osaka said after the victory. "I haven't played since May. I didn't know that. Somebody told me that. It's really good to be back."

Former world number one Osaka, whose ranking has slid to 41st, will play for a quarter-final berth against 18-year-old American sixth seed Coco Gauff, this year's French Open runner-up.

Gauff routed Ukraine's Anhelina Kalinina 6-1, 6-0 in 54 minutes.

Osaka's match marked the return of her father, Leonard Francois, as her coach. Osaka had been working with Wim Fissette for the past two years.

"It's good for him to be back because he always makes me smile," Osaka said. "It's just good to be back so I'm really happy."

In the first set of her return match, Osaka broke Zheng for a 2-1 lead, saved a break point to hold in the fourth game and held from there to capture the first set after 45 minutes with a service winner.

World number 51 Zheng broke for a 5-3 edge in the second set and held at love on a service winner to force a third set.

Osaka broke twice for a 4-0 lead in the final set, denied Zheng's fightback bid with a second-serve ace on a break point and held for a 5-0 lead.

After Zheng held, Osaka did the same to capture the match on a service winner after two hours and two minutes.

Reigning Wimbledon champion Elena Rybakina of Kazakhstan lost Monday in her first match since capturing her first major title, falling to 12th-ranked Daria Kasatkina.