"I am not 100 percent physically. I am a bit tired after competing in so many events at the meet ... everything now is about preparation and only the Olympics matter."

With four-time world champion Sjostrom recovering from an elbow injury, the 100m butterfly is now considered a wide-open race in Tokyo, with Australian sprinter Emma McKeon and rising American star Claire Curzan also within reach of the podium.

Still, Zhang is making no secret of her goal to bring home both golds, having swum 55.62 in the 100m－0.11 quicker than her Qingdao result－at a domestic meet in September last year.

"I went for the world record in the heats," Zhang said after the 100m preliminaries. "Although I didn't do it, knowing that I've got what it takes to be competitive at the highest level will help me stay composed at the Olympics."

Zhang's standout performance in Qingdao drew attention away from a rumored return of Sun, who is officially eligible to compete after having an eight-year ban by the Court of Arbitration of Sport (CAS) for an alleged doping violation overturned by a Swiss court in December.

Sun was suspended by the Lausanne-based CAS in February 2020 for refusing to cooperate during a random out-of-competition drug test in September 2018. That ruling was set aside by the Swiss Federal Tribunal following a successful appeal by Sun's legal team, which questioned the neutrality of Franco Frattini, chairman of the CAS panel that heard the case and issued the ban.

With his case to be heard again by a different CAS panel from May 24-28, Sun is expected to find out before the Tokyo Games open on July 23 whether he can compete at his fourth Olympics or instead retire in disgrace.

Sun won the men's 400m and 1,500m freestyle at the 2012 Olympics before adding a third gold in the 200m at Rio 2016 to become China's most celebrated swimmer until the doping case derailed his career.