Kvitova arrived for the match against the world No. 66 Siegemund as statistically the best server of this year's French Open remaining women's players, both in terms of ace struck and percentage of service games won.
Firmino doubled the hosts' lead by sliding home from close range after being fed by Atletico Madrid left-back Renan Lodi.
Turkey responded well and created two chances in quick succession through Efecan Karaca and Yusuf Yazici in the 15th minute.
The German coach has spotted a lack of mentality, but didn't mention the loss of efficiency and robustness.
Slovan Bratislava, one of the top title-contenders, was also close to losing its third in succession but managed to edge out Miskolc in OT to earn the first points of the season.
"The players don't seem worried, because unfortunately it is a situation that will last for a while. We'd all like things to be different and to be able to play with fans in the ground, but we can't be worried, even though we all want this to be resolved as soon as possible," said the coach in his pre-game press conference.
47-year-old Liu is in high spirits during her preparations for the upcoming Tai Chi exhibition in the city of Liling, located in central China's Hunan province.
Marcel Hascak and Patrik Svitana led the scoreboard with two goals each, Svitana added also two assists to put a silver lining to his exceptional performance and help his team climb to the second place in the rankings.
"A professional player's career could be short, but in this way, football will always be a part of my life," she said.
The UEFA Nations League is a new competition between national teams that replaced friendly matches which often lacked a competitive edge. It is entering its second season. The four group winners of the top-ranked League A qualify for the UEFA Nations League Finals in June 2021. For the remaining sides, there is promotion and relegation to play for. Enditem
Li Yueru shot 13 of 17 from the field to contribute 27 points and 20 rebounds for the winner. Shanxi was unable to contain Li Yueru's glittering play, thus seeing little hope of a comeback in the second half.