arsenal face chelsea at the emirates stadium on sunday afternoon .
cesc fabregas makes his first return to his former club in the clash .
arsenal manager arsene wenger wants fans to respect ex-players .
the gunners had the chance to re-sign fabregas but he went to chelsea .
wenger refuses to say if he regrets that but admits he wishes he never left .
read : arsenal can beat chelsea , says arsene wenger .
arsenal vs chelsea special : cesc fabregas makes emirates return .