Suwon Bluewings made a strong start to their AFC Champions League campaign by inflicting a first home defeat in almost two years on Sydney FC, while Chinese Super League sides Guangzhou Evergrande and Shanghai Shenhua were both held to 1-1 draws.
Two-time Champions League winners Suwon will have been expecting a challenge given Sydney's incredible record at the Allianz Stadium and their status as runaway leaders in their domestic A-League campaign, but ultimately it proved comfortable as they won 2-0 win on the road.
New signing Dejan Damjanovic broke the deadlock in the 62nd minute, finding the net in style from 25 yards and the Montenegrin doubled his tally soon after, converting a penalty after Brandon O'Neill was guilty of handling in the area.
Sydney could muster little response and ultimately suffered defeat at home for the first time in a competitive match since April 2, 2016.
Guangzhou made an underwhelming start to their Group G campaign, surprisingly drawing 1-1 at home to Thai side Buriram United.
Brazil international forward Ricardo Goulart - who incorrectly had an early goal disallowed - opened the scoring after 16 minutes, heading in an inch-perfect cross from the left wing.
But United showed admirable spirit and looked the better side in the second half, though they were unable to take all three points, settling for a point earned by substitute Edgar Silva's equaliser just before the hour mark.
Shenhua also started brightly away to Kashima Antlers, with captain Giovanni Moreno nodding in from close range in the third minute after a goalkeeping error.
The hosts secured a share of the spoils early in the second half, though, with Yasushi Endo bundling in from inside the six-yard box after a fine cross, ensuring Suwon finish matchday one top of Group H.
The day's late kick-off saw South Korea's Jeju United lose 1-0 at home to Cerezo Osaka of Japan in Group G, with a stoppage-time goalkeeping howler from Lee Chang-geun allowing Kota Mizunuma to tap in the winner.