Arsenal injuries: Per Mertesacker, Aaron Ramsey and Gabriel Paulista add to Arsene Wenger's injury crisis

The trio were forced off during Arsenal's 4-0 FA Cup victory over Hull on Tuesday night

Per Mertesacker suffered a cut and a small concussion after a head clash with Nick Powell (Getty Images)

Arsenal’s 4-0 FA Cup victory over Hull City came at a huge cost after manager Arsene Wenger saw three of his first-team squad come off injured, leaving him with a defensive crisis ahead of this weekend’s sixth round visit of Watford to the Emirates.

Strikers Olivier Giroud and Theo Walcott both scored at the KC Stadium to ensure the reigning FA Cup champions did not slip up in the fifth round replay, but Wenger will have concerns ahead of this weekend’s fixture after both Per Mertesacker and Gabriel Paulista were forced off with head and leg injuries respectively.

When the Brazilian limped off, Wenger was forced into a reshuffle, with Calum Chambers switching to centre-back and Mathieu Flamini moving to the right to accommodate substitute Ramsey. However, the Wales international had to leave the field 16 minutes after coming on after suffering a thigh injury just as Giroud scored the opener, and Wenger revealed that the midfielder could be set for some time out after suffering most out of the injured trio.

“It was a shock as we lost our two centre-backs in the game and then we lost Aaron Ramsey” Wenger told reporters after the match.

“Mertesacker is not serious, just a little concussion, and I think Gabriel looks all right but for Ramsey I am little bit more concerned.

“It's a thigh injury... but apart from that we have played well.”

Wenger admitted on Monday that his only other regular centre-back, Laurent Koscielny, was struggling with a minor injury and would be a doubt for this weekend’s encounter, having missed the FA Cup replay as well as last weekend’s north London derby with Tottenham.

Mertesacker attempted to carry on after a nasty clash of heads with Hull midfielder Nick Powell left both players bloodied, but the World Cup winner had to concede defeat shortly after the half-hour mark and Wenger admitted that he had suffered a “small concussion”.

Gabriel Paulista had to be taken off with a leg injury (Getty Images)

Aaron Ramsey was forced off 16 minutes after coming on as a substitute (Getty Images)

Alarmingly, at a time when brain injuries are dominating the headlines in football as well as other contact sports, Wenger’s claim that “it’s nothing serious, just a concussion” could well attract attention over the Frenchman’s lack of concern for head injuries.

It means that Arsenal now have nine injury concerns ahead of the Watford clash, with Santi Cazorla and Tomas Rosicky unlikely to play again this season. Jack Wilshere is yet to play a minute of football this campaign as he slowly recovers from a broken leg, while Petr Cech will be out until the end of the month at the earliest following a calf injury sustained in the defeat to Swansea last week.

Alex Oxlade-Chamberlain will not return until the end of April due to a knee injury, although Wenger could decides to rush back Koscielny in a bid to ease his defensive crisis this weekend. Should the Frenchman fail to regain his fitness, Wenger is likely to turn to natural left-back Nacho Monreal to fill in at centre-back, with the Spaniard losing his place in the flank to Kieran Gibbs this week.