Stage One involves 32 groups of four players, with the player who tops each group progressing to Stage Two.
Multiple Chinese media outlets revealed that Tencent Sports would pay 10 million U.S. dollars for the one-year contract.
The "BVB" smoothed the way for their win with three first-half goals, while Dominic Volkmer's red card before half-time left Duisburg hopeless.
In the women's draw, US Open quarterfinalist Elise Mertens of Belgium disposed of Chinese Taipei's Hsieh Su-Wei 6-3, 6-1.
Clemens Wickler and Julius Thole from Germany are also the favorites for the EuroBeachVolley 2020 gold.
Cologne came out highly motivated after half-time and dominated proceedings, but still the "Billy Goats" squandered a number of chances.
Valencia got a flying start to the season a week ago when they twice fought back from behind before winning 4-2 at home to Levante, and another fightback looked to be on the cards when Maxi Gomez scored an impressive goal in the first minute of the second half following a pass from Daniel Wass.
In the 80th minute, with the assistance of Jean Evrard Kouassi, Eddy Gnahore slotted home with a goal for Zall to narrow the gap to 2-1 and had to settle with the score.
Xiao, world number 31, turned pro in 2007 after winning the Asian U21 Championship. His best ranking performances were runner-up finishes at the 2013 Shanghai Masters and the 2017 Shoot Out.
"We've taken note of all of his personal and technical characteristics as well as watching him play," Tite told a virtual news conference. "He is a new emerging talent in an important position," he added.
The hosts almost made it four moments later but Matthias Ginter hacked Felix Passlack's shot off the goal line.