The major riddle that Roberto Di Matteo must resolve over the coming weeks is: how can Barcelona be beaten. The only help he got with answering that here was: not by playing like this. A late goal by Juan Mata, following a contentious second-half strike from Branislav Ivanovic, gave Chelsea three valuable points from a low-rent performance. Wigan, who had seemed on course for a draw after Mohamed Diamé equalised in the 82nd minute, are unlucky to still be in the relegation zone.Chelsea' pursuit of Champions League qualification through the domestic route received boost before kick-off by the news that Tottenham Hotspur had dropped points in S...