The Hammers got back on the winners list with a hard-fought 2-1 victory over Hull City on Wednesday night following a three-game losing streak.
That triumph put them eight points clear of the relegation zone and although another victory over Sunderland on Monday night would have them further ahead of the 19th-placed Black Cats, Downing is taking nothing for granted.
"We should just get as many wins as we can on the board," he said.
"Don't think one more game will be enough because we could easily get dragged back in again.
"It will be massive for us if we beat Sunderland. They've got games in hand, but difficult games.
"They need points desperately and if we can get a win it probably deflates them a little bit."
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