Guardiola's men suffered a shock 3-1 loss to Lyon to end their European dreams for another year despite being among the favourites to lift the famous trophy this season, and Toure says their failure to perform in the competition was "strange".
"The manager has been signed for that, just to bring this trophy and when you see Liverpool maybe and other clubs who [have won it] without doing a lot of work in the transfer market, it's quite strange and disappointing," he said on Football Daily.
"Of course, he's been brought to the club to get a massive trophy for them and at the moment it's not been delivered in the way they want.
"Everyone knows Pep is a great manager but at the moment when things are not going their way, sometimes it's the time to change the way they do things. We'll see."