Cape Town - Wayne Rooney's winning goal against CSKA Moskow served to spare Louis Van Gaal from the wrath of Manchester United fans.
The fans at Old Trafford aimed a volley of boos in his direction when he replaced Anthony Martial with Marouane Fellaini in the 66th minute.
"Of course I heard it. I'm not deaf," Van Gaal said.
"It's just the opinion of the fans. But after they shall not be disappointed by the decision of the manager."
The United manager might not have been able to shrug the incident off so easily had it not been for a goal-line block moments before Rooney's goal by Chris Smalling, who slid in to clear Seydou Doumbia's goal-bound shot after the CSKA substitute had been denied by goalkeeper David de Gea.
Van Gaal acknowledged the importance of the England defender's intervention, but not for the first time referred to him erroneously as 'Michael'.
"Doumbia, that was the only attack of CSKA Moscow (when) a player of Manchester United stepped in on the wrong way," said Van Gaal, whose side now lead PSV Eindhoven and Wolfsburg by a point.
"And then David de Gea has saved us and after that Michael Smalling has saved us. But that's also football, that you are running everything out of your body to prevent goals.
"It is fantastic to see that Smalling is doing that."