Madrid: Catalan football giants Barcelona need to put an end to a run of disastrous results when they entertain Valencia on Sunday or run the risk of seeing their lead at the top of the La Liga evaporate completely. Three weeks ago Barcelona were 11 points clear of Atletico Madrid and 12 ahead of Real Madrid and it looked certain they would celebrate the title, reports Xinhua. After a run of one draw and two defeats later, one of them at home against Real Madrid, that lead could disappear entirely by the time they kick off on Sunday if Atletico win their home game against Granada. Not only has that spell seen their lead in the league reduced, but Wednesday also saw Barcelona knocked out of the European Champions League by Atletico Madrid in a game in which their rivals looked comfortable from start to finish. Barcelona head coach Luis Enrique has maintained that there is no problem, but stories have emerged of a possible breakdown in relations between him and key players in the wake of last weekend's 0-1 defeat away to Real Sociedad. Dani Alves hardly aided matters on Friday by publishing a video in which the Brazilian defender wore a wig and told fans not to worry about the Champions League exit because it was "just a game of football", in a video that has been roundly criticised. However, the coach's main problem is Argentine star forward Lionel Messi, who has not scored in five games since the international break in March and looks tired and flat. Messi's creativity and goals have papered over the possible cracks in some displays this season, but with his magic missing, those cracks have appeared. Meanwhile, neither Neymar (perhaps influenced by contract talks and the recent disclosure of his massive contract at the club) has been off form, nor is Luis Suarez at his best. Enrique needs them all on Sunday night against a rival which last weekend claimed a morale boosting win at home over Sevilla to virtually assure their top-flight status after a difficult season, because if Barcelona don't win, the season is in danger of falling apart.