Austin, Texas — Jordan Spieth had another stress-free day in the Dell Match Play and avoided the drama that the 18th hole provided Thursday.

Spieth again built a big lead and had no trouble against Victor Dubuisson of France. With two victories, Spieth only needs a halve against Justin Thomas in the third round to advance to the round of 16 at Austin Country Club.

Jason Day ended any suspense about his back injury by playing, and then driving the green on the 381-yard opening hole.

Serena Williams beats McHale at Miami Open

Key Biscayne, Fla. — Serena Williams began her bid for a ninth Key Biscayne title Thursday by beating fellow American Christina McHale 6-3, 5-7, 6-2.

Williams, seeded No. 1, earned her 19th consecutive victory in the tournament and hasn’t lost since the 2012 quarterfinals.

Facing McHale for the first time, Williams converted only five of 17 break-point chances. She let a match point get away in the second set and had to play for an additional 50 minutes to improve to 12-2 this year.

China admits 6 positive tests in swimming; denies cover-up

Beijing — The China Anti-Doping Agency says there have been six recent positive drugs tests by Chinese swimmers but denies claims in a British newspaper of a cover-up.

The Times said in Thursday’s editions that it had been approached by whistleblowers in Chinese swimming who claimed that five positive tests had been kept secret.

Zhao Jian, deputy director of the Chinese agency known as CHINADA, said it had recorded three positive tests, all for clenbuterol, in late August and early September.

The swimming federation will soon issue punishments in those cases and the results will be made known.

Zhao said there have also been three positive tests since the beginning of 2016, all in January, but those remain under investigation and will be publicized within 20 days of punishments being issued in accordance with WADA regulations. He said the World Anti-Doping Agency has been kept informed about all positive tests.