MADRID. Barcelona begin the defence of their La Liga crown on Sunday amid doubts over the strength of their backline, Neymar’s adaptation to European football and how new coach Gerardo ‘Tata’ Martino will perform.

Argentine Martino was a surprise choice to replace Tito Vilanova, after Pep Guardiola’s former assistant suddenly announced he was to step down due to ill health just before the start of the pre-season a litle over three weeks ago.The 50-year-old moved from Lionel Messi’s former club Newell’s Old Boys to his first European post as a disciple of the club’s possession-based style of football.Although relatively unknown in Spain, his low-key approach appears to have won over the senior figures in the dressing room."He is a leader, capable, well-prepared and experienced,” midfielder Xavi told newspaper Sport this week. "He has very clear ideas and is very precise in what he wants."We are recovering a little the intensity and rhythm that perhaps for diverse reasons we lost towards the end of last season.  "The philosophy remains the same.”Martino takes charge of a settled and experienced side who equalled the league record points haul of 100 to win the title last season, their fourth in five years, and little has changed in terms of personnel.Neymar promiseStriker David Villa has left for Atletico Madrid and midfielder Thiago Alcantara for Bayern Munich, but the €57 million capture of young Brazil forward Neymar promises plenty of excitement up front.The 21-year-old has scored a couple of goals in pre-season friendlies and looked lively linking up with his teammates, albeit against mediocre opposition.How the slightly-built Neymar will fare in more physically-demanding matches remains to be seen as Barca persist with a forward line consisting of pint-sized technical wizards with Pedro, Alexis Sanchez and Messi completing the strike force.Cesc Fabregas continues to search for a settled role within the team, but it is Barca’s failure to land a central defender which has captured most of the pre-season headlines.The Catalans tried and failed to lure Brazil’s Thiago Silva away from Paris St Germain and have been told by Chelsea and Liverpool respectively that David Luiz and Daniel Agger will not be moving either.Time is running out as the transfer window draws to a close and their surprisingly poor handling of the search leaves Barca contemplating the campaign with the thinnest of resources at the back.France left back Eric Abidal, who could cover in the centre, was not offered a contract extension and has left, while injury-prone captain Carles Puyol, who turns 36 during the season, still has not returned from knee surgery.Only PiquéThat leaves Gerard Pique as the only specialised centre back in the side, supported by Argentina’s converted midfielder Javier Mascherano.To date, the club have shown little faith in their youth team product Marc Bartra, though Martino has been impressed with another youth team player, 18-year-old Cameroonian Frank Bagnack.For a side expected to compete on every front it is a risk to have to rely on cover from Cameroon midfielder Alex Song, Brazil full back Adriano and even Spain midfielder Sergio Busquets in the centre of defence.Latest reports are that Martino has said he is happy with what he has for the moment after a whirlwind induction to the club, and would prefer to take his time to choose a signing if he deems it necessary.After a disrupted pre-season that included trips to Israel, Palestine, Thailand and Malaysia and few games against tough opposition, Martino’s Barca approach Sunday’s visit of Levante without the best preparation.Next week’s Spanish Super Cup first leg away to King’s Cup winners Atletico will be a sterner test, but after consecutive seasons where the league champions have racked up 100 points, a slow start and dropped points could quickly prove decisive in the title race.