By Tom Gott Xavi has challenged Barcelona president Joan Laporta to reveal the reasons behind his upcoming exit. Less than one month after reversing his decision to step down this summer, Xavi was relieved of his duties on Friday after public criticism of the club’s current situation angered Laporta. Xavi will, however, remain in charge for the final game of the season against Sevilla on Sunday, before which he sat down in front of the media for his usual pre-match press conference. Asked what explanation Laporta had given him for his decision, Xavi insisted: “I think it is a question that he …