Barcelona facing defensive crisis ahead of El Clasico after Thomas Vermaelen injury

Barcelona are facing a defensive crisis ahead of next week's games against Sevilla, Inter Milan and Real Madrid after Thomas Vermaelen was ruled out for six weeks.

Vermaelen injured his hamstring while on international duty with Belgium and returned to Barcelona for tests on the problem over the weekend.

The club confirmed on Monday that he will be sidelined for the next month-and-a-half, which could see him miss up to eight games.

Ernesto Valverde is already without Samuel Umtiti, with Barca refusing to put a timeframe on the defender's recovery from a knee injury.

Umtiti has not played since the end of September and reports in the last week suggested he might need surgery, which could keep him out until 2019.

Gerard Pique and summer signing Clement Lenglet, therefore, are the only fit centre-backs Valverde has at his disposal.

Lenglet, who was sent off on his full La Liga debut, is still adapting to his new surroundings, while Pique has made high profile mistakes in the club's four-game winless run in the league.

Barca have already conceded nine goals in eight games this season -- the same amount they conceded in their opening 20 fixtures in the last campaign, and are also suffering from a lack of depth in the full-back positions.

Right-back Sergi Roberto has missed the last two games with a muscle injury, but he could return in the next week.

Jordi Alba has no understudy at left-back following Lucas Digne's summer move to Everton.

With just four fit defenders as things stand, Valverde may have to look to the reserve team for reinforcements.

Left-back Juan Miranda and centre-back Jorge Cuenca are the most likely to make the step up if needed.

Barca host La Liga leaders Sevilla on Saturday and then welcome Inter to Camp Nou in the Champions League the following Wednesday, before hosting Madrid in El Clasico on Oct. 28.