Al Duhail opened the scoring in the 12th minute as Abdullah Al Ahrak cut inside from the right flank and unleashed a powerful drive from 25 yards that nestled into the roof of Adel Al Hosani's net.
Fourth-seeded Matteo Berrettini outlasted Stefano Travaglia 7-6 (5), 7-6 (1) in an all-Italian contest to reach the last eight.
More than other clubs, Schalke has suffered from games behind closed doors. "Schalke is a club with a very close connection to its enthusiastic fans. To play without them feels strange," he commented.
Suarez was not included in the squad for the game and the first question Koeman had to field from Catalan TV network, TV3 was about the striker as the Uruguayan continues to train apart from the rest of the squad ahead of a possible transfer.
The South American qualifiers had been due to begin in March but were suspended because of the global health crisis.
To survive the club's crisis, Schalke turned to wage cuts, part-time work for employees, and a 30 to 40-million-euro loan from the federal state of North-Rhine Westphalia.
"When the years are passing, you are trying to win as much as you can - and when you win, you want to win more. I think this club describes what I am as well; I want to achieve all of the goals, win as many trophies as possible," said the midfielder.
Tencent Sports, a subsidiary of Chinese internet giant Tencent, will broadcast all 372 remaining matches from the second round of Premier League which are scheduled to start on Saturday.
The 79,000-seat Maracana, which hosted the World Cup deciders in 1950 and 2014, was this month described as having the worst playing surface in Brazil by Flamengo vice-president Marcos Braz.
Thiago's arrival will give Liverpool further midfield options and variety alongside Jordan Henderson, Georginio Wijnaldum, Naby Keita, Fabinho, Alex Oxlaide-Chamberlain and the veteran James Milner, although Barcelona are rumored to be interested in taking Wijnaldum to the Camp Nou. Enditem
Despite Thursday's result, Flamengo are second in their Libertadores group with six points from three matches but with a negative goal difference. The Rubronegro remained in Ecuador after the clash in Quito to prepare for Tuesday's fixture against Barcelona SC in the Pacific port city of Guayaquil.