She will take on 15th-seeded Maria Sakkari of Greece in the last 16, who stunned Williams at the Western & Southern Open last month.
Indeed, before the enforced break due to the coronavirus, Atletico were in sixth place in the table and it looked as if a top-four spot and qualification for the Champions League were in doubt.
World championship leader Lewis Hamilton could only finish seventh after serving a time penalty for coming into the pitlane when it was closed, dropping him to the back of the field.
Patrick Bezerra equalized eight minutes later with a header following Thiago Galhardo's cross.
However, he was very critical of Bartomeu, accusing him of "not keeping his word" and also criticizing the direction of the club in recent years.
In the other two matches of the day, Hunan Hualai survived an intense battle to overcome Xiamen Tefang 3-2, while Jiangsu Weikeduo lost to Zhejiang Nengyuan 4-1, and remain at the bottom with no wins. Enditem
The veteran opened the score by firing a freekick before the break, then added a second by curling home from the edge of the penalty area in the 73rd minute.
The under-23 striker Zhang proved his worth again in the 44th minute, as he tapped Jonathan Viera Ramos' cross home to add another goal for Guoan.
"Now the games are less, for me the time for the preparation is not the best, I had only two weeks,"
Chang'an Athletic is in Group B with Meizhou Kejia, Guizhou Hengfeng, Zhejiang Greentown, Liaoning Shenyang and Jiangxi Liansheng. All the Group B matches will be played in Meizhou, Guangdong province.
"I was playing well today," said Thiem. "I had a good plan for the match. He's very dangerous when he can dictate with his forehand. I was exactly trying to avoid that. He also has very, very fast legs. I was trying to play my fastest tennis to keep him on the backhand, to not let him dictate with the forehand."