Title races can be tense, tight encounters at the best of times, without the referees making life even more difficult for the chasing pack. One slip up in the business end of the season, and the league crown could slip through your fingers like grains of sand. Which is probably why Sir Alex Ferguson was so enraged when Didier Drogba's offside goal was allowed to stand in 2010. In April, with just five games left to play, Chelsea took on Manchester United at Old Trafford with both sides in with a chance of winning the title. The game was finely balanced at 1-1 with 11 minutes remaining, after Joe Cole and Federico Macheda had netted in the first and second halves. Then, Salomon Kalou put Drogba through, the Chelsea striker was clearly offside but Deans assistant, Simon Beck, didnt spot it. The game finished 1-2 to the Blues, who won the Premier League that season - yet may not have done so had it not been for this ill-judged decision.