Arsenal will be without Samir Nasri and Jack Wilshere.
Nasri is on the brink of joining Manchester City, while Wilshere is ruled out after suffering a setback in his recovery from an ankle problem.
Also missing will be Laurent Koscielny (back), Nicklas Bendtner, Abou Diaby (both ankle), Kieran Gibbs (hamstring) and Sebastien Squillaci, but Tomas Rosicky, Johan Djourou and Armand Traore are fit, as are Alex Song, Gervinho and Emmanuel Frimpong amid their domestic suspensions.
Udinese coach Francesco Guidolin has a few injury concerns to leave him further short-handed on Wednesday night.
After missing the first leg through injury, striker Antonio Floro Flores is set to miss out again while there are further problems in defence. Centre-half Maurizio Domizzi has been ruled out with a thigh problem while right-back Dusan Basta is also a doubt.
Arsenal (from): Szczesny, Jenkinson, Vermaelen, Djourou, Sagna, Traore, Arshavin, Frimpong, Ramsey, Song, Rosicky, Walcott, Van Persie, Fabianski, Chamakh, Oxlade-Chamberlain, Gervinho, Miquel.