Esteghlal had been linked with former Werder Bremen coach Alexander Nouri but they failed to reach an agreement with the German-Iranian coach due to financial disagreements.
"We are in a very strange situation, after a lot of months without much tennis, especially for me, that I didn't play in America, I don't know if it's a positive thing or a negative thing," Nadal said when asked how important it was to keep the early-round matches short and sweet.
With Sichuan's offense bogged down, Dongguan retook the lead and delivered the final blow with efficient offensive late in the fourth to make it 78-71.
Julian Draxler, Idrissa Gueye and Kylian Mbappe added another three in the second half while Angers pulled one back in the 52nd minute.
Next up for Halep is another 19-year-old youngster, Iga Swiatek of Poland, whom Halep defeated in the round of 16 here last year.
Tsitsipas was edged by Stan Wawrinka in a marathon over-fiver-hour battle at this stage last year, but this time he took chances with his 24 winners against the No.18 seed.
Jose Bordalas' men now travel to play Real Sociedad - one of the most attractive sides in La Liga, but who have struggled for form at home since the return of football in June.
"It is a very difficult group with Leipzig as the third seed," Tuchel said. "We know how strong they are. We will need to be at our best to go through." Enditem
The 51-year-old coach replaced interim coach Majid Namjoo Motlagh on the Tehran-based team.
The Buenos Aires giants confirmed the move via a brief statement on social media, in which they wished Marcone "many successes in this new stage".
Dilana took center stage early on by scoring seven points in a row, while Yang Shuyu provided much-needed help beyond the arc. The duo combined for 17 points in the first quarter to propel Dongguan to a 22-13 advantage.