A crowd of 39,223, well short of the 55,000 capacity, watched the routine 4-0 win over the 10-man Cottagers.
After that game, Guardiola said: “Motivation was right and hopefully in the next game against United, our fans can come and make the stadium full.
“It was not full. I don’t know why. (Wednesday) gives a chance to go back to Wembley. Hopefully they will support us more.”
When it was put to him the financial demands placed on football fans, Guardiola said on Tuesday: “I understand the fans. It was never my intention to offend them. It’s so nice to have the fans here. I am always grateful for their support.
“Since I arrived here until the last day I want to fight to play as well as possible and see the Etihad full for every game.”
Guardiola remains wary of the threat posed by Manchester United in Wednesday’s League Cup semi-final second leg after his side were beaten 2-1 at the Etihad in the Premier League earlier this season.
“It’s Manchester United. They can do it, they have done it,” said the City boss, whose side hold a 3-1 lead from the first game at Old Trafford.
“In these kind of games against incredible teams with incredible history, they have pride and I know how difficult it will be to reach the final.”
