Sir Alex Ferguson believes that the future of both Manchester United and Rangers in the Champions League will be decided by group rivals Stuttgart's progress in the tournament.
United are well-placed to mount a challenge for top spot in the group and a favourable draw for the knockout phase after beating Rangers at Ibrox, but the threat of the German side remains.
Stuttgart followed up their victory over United earlier this month by overcoming Panathinaikos at home and if the Germans can repeat their success in Athens in a fortnight that will be bad news for the two British sides.
Ferguson said: "The key games are the next ones. The important thing is what happens in Greece and both Rangers and ourselves will be hoping Panathinaikos take something from their game there with Stuttgart.
"Stuttgart are a very difficult proposition on their own ground and if they get a result in Athens against Panathinaikos we are both going to be looking over our shoulder."
Phil Neville's fifth-minute individual goal secured a narrow victory for the English champions against their Scottish counterparts and the United player secured himself the 'Battle of Britain' ace tag with a goalline clearance too.
Ferguson added: "We always believed that both our games against Rangers would be tough and this game has just reinforced that.
"They have good players. Peter Lovenkrands is a great danger - he is quick and players who are quick can get behind you."
"With their tradition Rangers were never going to give up - a lot of European teams would not have shown the resilience that Rangers did. That is a British spirit thing.
"Winning 1-0 is a very dodgy result, you never know what is going to happen so we are relieved and satisfied.