A victory for City over United tomorrow night at Old Trafford will see them replace Liverpool on top of the table.
United will return to the top-four if they win, but Walker says some fans might be willing to sacrifice points in order to prevent Liverpool from winning the title.
"United fans are in a difficult situation obviously," the City right-back said.
"When I'm out and about or walking my dogs, United fans are coming up to me saying, 'We'd rather City win the league than Liverpool'.
"It's strange to hear but I can assure you the United players aren't going to leave a red carpet and say, 'Go on City, score past us'.
"They're going to make it difficult because it's a game of football and they're fighting for the top-four as well so they need the points."