Former QPR star Martin Allen feels Arsenal's lack of steel was exposed at Liverpool.
Mad Dog wrote in the Daily Mail: "When you compare Wenger's side now to the The Invincibles of 2003-04, they played similar fantastic football, but their two centre-backs of Sol Campbell and Kolo Toure and two centre midfield players of Patrick Vieira and Gilberto Silva were men made of steel.
"They had a winning mentality and in the face of the fiercest storms they could go toe-to-toe and trade blows with the toughest opponents out there.
"At the moment Arsenal are lightweight in that area and I doubt they can challenge for the top spot."