The teenage midfielder will miss training on Sunday after picking up an ankle knock during the Gunners' goalless draw with Sunderland, adding to manager Arsene Wenger's injury concerns. Winger Theo Walcott and striker Robin van Persie are already on the casualty list and will be absent for the second leg of the last-16 tie at the Nou Camp, while captain Cesc Fabregas faces a race against time to be fit for the showdown after suffering a hamstring problem. And with defensive midfielder Alex Song also doubtful, Wilshere's injury has come at a problematic time for the Gunners as they look to build on a 2-1 first-leg advantage in Spain. Wenger said: "Wilshere has an ankle problem and we'll wait until Monday or Tuesday to see if he's back." Another player who will be unavailable on Tuesday is defender Thomas Vermaelen, who has been ruled out since August with an Achilles injury. However, Wenger has more defensive options at his disposal than he did for Arsenal's win in the first leg, when he was without two centre-backs as well as Song. The French boss feels a flawless defensive display will be key against Barca if the Gunners are to advance to the quarter-finals. "It will be very important for us to defend well because when you go to the most effective attacking team in the world, you want to have your best defenders available," he said on Arsenal's official website. "We will look to defend well and attack well. We are not a team that will refuse to attack, we know that. "The challenge will be to find the right balance between having a team who can defend, as well as one that has a good opportunity, every time it has the ball, to go forward."
