Barcelona are facing a defensive injury crisis, with Thomas Vermaelen having been ruled out for up to six weeks with a thigh complaint.The 32-year-old has endured a series of fitness issues throughout his time at Camp Nou, and is now facing up to another spell on the sidelines.He was forced off during a recent outing for Belgium against Switzerland and was removed from Roberto Martinez’s squad as a result of that knock. Article continues below Editors’ Picks Man Utd ready to spend big on Sancho and Haaland in January Who is Marcus Thuram? Lilian’s son who is top of the Bundesliga with Borussia Monchengladbach Brazil, beware! Messi and Argentina out for revenge after Copa controversy Best player in MLS? Zlatan wasn’t even the best player in LA! Subsequent scans have confirmed that the former Arsenal man is set to be kept out of action until December.A statement released by Barcelona on their official website read: “The tests carried out on Monday confirmed that first team player Thomas Vermaelen has an injury to the femoral biceps of his right leg. Approximate down time is six weeks.”Vermaelen will now play no part in Belgium’s upcoming friendly clash with the Netherlands on Tuesday.He will also be unavailable to Barcelona for the foreseeable future, leaving them alarmingly short on centre-half options.World Cup winner Samuel Umtiti has already been ruled out for the long-term with a knee problem .He has been missing since September 26 and no timescale has been put on his recovery, with those at Camp Nou waiting to discover how he responds to treatment before pencilling in a return.With Vermaelen now in a similar position, Ernesto Valverde has just two fit options available to him at the heart of his back four.Gerard Pique and Clement Lenglet are proven performers at the highest level and are more than capable of covering for absent colleagues, but they cannot afford to pick up any knocks of their own.Barca, who headed into the international break on the back of a four-match winless run in La Liga, have a number of testing fixtures to come before the end of the calendar year.They are set to return to action on Saturday against Sevilla, before then playing host to Inter in the Champions League.A first Clasico clash of the 2018-19 campaign will then see them welcome arch-rivals Real Madrid to Camp Nou on October 28.Before the likes of Umtiti and Vermaelen come back into contention, they will also have to take in meetings with the likes of Atletico Madrid, PSV, Villarreal, derby foes Espanyol and Tottenham.