Del Bosque is thought to be considering multiple changes to his starting XI following last week's 5-1 thrashing by the Netherlands.
However, Fabregas does not believe that there will be too many new faces when the team takes to the pitch in Porto Alegre.
"The boss will have his ideas about what he has to change and what he will leave the same but I don't think there will be a huge amount of changes because I think this side has shown how good it is," he told Movistar.
"We are positive, even though it has been hard. I see the side fully focused on what they have to do, training well, with the right mentality. We have to win and get the three points, which are vital."
Fabregas came off the bench for Spain during their heavy defeat to the Dutch.