Bayern Munich manager Pep Guardiola expects to face a compact Arsenal in the Champions League on Wednesday night, but said forcing the Gunners to play long balls out of the back would give the Germans a chance to control the game. Bayern host Arsenal at the Alliance Arena having lost at the Emirates Stadium two weeks ago in their only defeat of the season so far and, based on what he saw in England, Guardiola said the Gunners would defend deep and rely on striker Olivier Giroud's hold-up play to keep themselves in the game. Arsenal need at least a point in Germany to keep qualification for the knockout stages in their own hands, and Guardiola plans on targeting Per Mertesacker, who he views as the weakest link in the Premier League side's back four because of his lack of pace, if the German starts. 'Arsenal want to attack and build up, but when you press Mertesacker or (Laurent) Koscielny they don't want to play,' Guardiola told reporters in his pre-match news conference. 'They play long balls to Giroud and if they win these balls they can play with (Santi) Cazorla, with (Mesut) Ozil, with Alexis (Sanchez). 'But if they lose the ball and we make two or three passes Mertesacker doesn't want to stay up high so they go back in their box and defend there. 'Arsenal will defend deeper than they did in London, as Mertesacker prefers to defend in his own box than further forward,' Guardiola added. 'Petr Cech will not play the ball to defenders, but will try long balls to Giroud. We have to defend well and be ready for that.' Guardiola's assessment of how the tie would shape up was all but confirmed by Arsenal boss Arsene Wenger, who stressed the importance of a solid defensive performance during the game. 'Defensively discipline will be vital tomorrow. We need to manage a good balance between being committed and not giving fouls away,' the Frenchman said The Gunners are in the middle of an injury crisis and are currently without nine first-team players including Aaron Ramsey, Theo Walcott, Alex Oxlade-Chamberlain and Jack Wilshere. Right-back Hector Bellerin is also out of Wednesday's clash with a groin problem, with Wenger confirming that Mathieu Debuchy would start in his place.