Despite starting all three Primera Division games so far this term, Fabregas remains far from happy playing a cameo role for his boyhood club, having returned to the Nou Camp last summer for £30million after eight years at Arsenal.
He told Radio Marca: "There's no such thing as a great substitute in the world of football.
"I couldn't tell you what makes a great substitute.
"I always wish my team-mates well and put a happy face on.
"If I have to take my unhappy face home then so be it, but I would never let my team-mates or manager see it."
The versatile 25-year-old competes for a starting berth in the centre of the park with Andres Iniesta, Xavi, Sergio Busquets and new recruit Alex Song, his former Gunners team-mate.
"Everybody likes to play every minute of the season," he added.
"I've always said that I play for the best team in the world, but I came here to compete, to learn and enjoy, not to sit wracking my brains.
"The manager knows what I can offer. But across the three positions that I can play, I am competing with the three best players in the world.
"I'm delighted to be a part of this team but when a coach tells me I have to go, I'll go.
"But I will not make it easy for him to do so, by any means. I will keep going, looking forward to the time that things change.
"I came here to see out my career."
Fabregas' apparent malaise echoes that of Real Madrid forward Cristiano Ronaldo, who refused to celebrate his brace against Granada due to feeling "sad" for "professional reasons".
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