The Reds are two points behind United on the top o fthe table, but the Red Devils also have a game in hand.
“I take my hat off to United. They have showed scary strength and have many strings to play on,” Agger told Ekstra Bladet.
“They are the most stable and they win the close games.”
“If we want to keep our chances for the trophy alive we can’t draw in so many games,” added Agger.
“Manchester United could be five points ahead of us if they win next Wednesday’s game against Fulham.
“Because of that we will have to beat them at Old Trafford.”