Mourinho lost his job in December last year after overseeing a poor stretch of form and poor results despite being the club's most successful manager in it's 110 year history winning three league titles, FA Cup, Community Shield and three League Cups.
Fabregas, who insists he remains on good terms with Mourinho, says he and his Chelsea team-mates were to blame for taking advantage of Mourinho's trust.
“I have huge respect for him, we still keep in touch right now,” Fabregas said on Sky Sports’ Monday Night Football. “The biggest problem was he trusted us too much, gave us more holiday because we were champions and we let him down. That was the main reason he had to go – and for that myself and the team feel bad for it.”