Former referees Howard Webb and Keith Hackett have said Manchester United's Wayne Rooney should have been booked against Liverpool while the home side's equaliser should not have stood.
Zlatan Ibrahimovic headed home in the 84th minute to cancel out James Milner's first-half penalty as Sunday's match ended 1-1 at Old Trafford.
Ibrahimovic's leveller came after Antonio Valencia had strayed into an offside position in the build up, while Rooney had earlier conceded a free kick after catching Milner with his studs but was not cautioned by referee Michael Oliver.
Webb, who refereed the finals of the World Cup and Champions League in 2010, said in The Times: "I think Wayne Rooney's tackle on James Milner, for which Michael Oliver gave a foul and no more, is one of those that is somewhere between a red and a yellow card.