The Belgian - named the Footballer of the Year last season for his superb displays in helping Chelsea win the Premier League title - has still been subjected to some withering criticism from his own supporters in the wake of Mourinho's departure.
He was named as one of the alleged 'rats' who cost Mourinho his job, and Hazard has now acknowledged feeling guilty at his poor displays this season.
"I sent him (Mourinho) the message to say I was sorry he had gone and, well, just that I was sorry," Hazard told The Guardian. "We'd enjoyed all that success together last season, but this time round we hadn't.
"I felt a little bit guilty because I'd been player of the year. I'd been one of the most decisive players, and this year I'd performed less well.
“I hadn’t been at the same level. So I sent that text to José and he came back to me, wishing me all the best for the future. For a team of champions to go through what we have this year even I can’t explain.
"Things have been better recently, but we’re still not winning games quite as we used to. No one can put his finger on what’s happened at Chelsea.”
Hazard - who has been linked with a move to Real Madrid - scored his first goal of the season in the FA Cup win at MK Dons last weekend, and hopes that signals a change in fortunes.
"You can’t escape you’ve not scored and it’s already January, so last Sunday was a bit of a relief," he added. “I don’t think my morale was down, but it plays on your mind a bit. Everything went so well in the past. This year, not so much.
"But you have to tell yourself that football is like that. I’ve had more ups than downs in my career. All you can do is keep working. You still have to take enjoyment out of what you’re doing and things will turn, and my smile has always been there. In good moments and bad.
"I’m somebody who can laugh even at myself. That happens now and again, when I’ve made a mess of really simple things. I say to the other guys in the dressing-room: ‘Bloody hell, did you see what I did then?’"
How it all went wrong for Jose Mourinho
- Telegraph