Guangzhou stunned Japanese treble winners Gamba Osaka 2-0 in their Group F opener last month but then lost 2-1 at home to Thai champions Buriram United two weeks ago.
On Tuesday third placed Guangzhou welcome second placed Seongnam (both on 3 points) to Yuexiu Stadium and coach Contra feels that this is a big game for his side.
"This is a crucial match for us," said Contra.
"If we can't win this game, we will have serious problems of qualification.
"We don't want to lose again at home. We have to fight for the ball. We've lost two home games in a row; we can't afford to lose one more."
Seongnam coach Kim Hak-bum's side lost to domestic champions Jeonbuk Hyundai Motors since their last outing in the AFC Champions League but did beat Japanese champions Gamba 2-0 at home two weeks ago.
"We are well prepared and I am quite confident. We are looking forward to it. R&F is a strong opponent, I have every reason to believe it will be a good game," said Kim.
"The humid weather is an objective factor that is out of our control, I just hope my players can do their best.
"We know that R&F played their domestic game on Friday, and we played one day later. It is important that we recover quickly from fatigue. We will focus on recovering and getting ready for the match," he added.