Soccer:Arsenal manager Arsene Wenger has let Andre Santos know that swapping shirts with Robin van Persie midway through Saturday's defeat to Manchester United was unacceptable.

The Brazilian left back was team-mates with Van Persie until the striker’s acrimonious departure to Old Trafford during the summer.

Santos endured a torrid time against United and also came under scrutiny for exchanging shirts with the Dutch international at half-time of a game in which Arsenal slumped to a 2-1 defeat.

Reports suggested Santos could be dropped from tomorrow’s Champions League tie at Schalke as a result but, while angry with the player, Wenger was keen to downplay the incident.

“I spoke about that but I don’t want to make too much of a big story of that,” the Arsenal boss said.

“I believe that was not the right thing to do at all, but that is not an explanation for our bad performance on Saturday.”

Meanwhile, Theo Walcott will be assessed tomorrow to see if he is well enough to feature in Germany.

The 23-year-old has been ill overnight and is a doubt for the Group B encounter, which will not see the return of Wojciech Szczesny (ankle) despite the goalkeeper joining in with training today.

Aaron Ramsey misses out after sustaining a groin injury in Saturday’s defeat at Manchester United and is joined on the sidelines by Alex Oxlade-Chamberlain (hip), Gervinho (ankle), Kieran Gibbs (thigh), Abou Diaby (thigh) and Tomas Rosicky (hamstring).

Provisional squad: Mannone, Shea, Sagna, Vermaelen, Arteta, Djourou, Mertesacker, Koscielny, Wilshere, Giroud, Cazorla, Santos, Podolski, Walcott, Arshavin, Jenkinson, Coquelin, Chamakh.