The Belgian wideman has been strongly linked with a move to Paris Saint-Germain but the Chelsea manager has reiterated his desire to keep him no matter what the offer.
Reports in France have suggested Paris Saint-Germain is extremely keen to sign the winger, but Mourinho has quashed such speculation, saying he wouldn't even sell the 23-year-old for "crazy" money.
Instead, Mourinho lavished praise on a player who has gone through a "fantastic evolution" since the Portuguese returned to Stamford Bridge last summer.
"He has made progress in everything. He was known as one of the worst trainers. Now I would not say he is one of the best but he has become a good professional," the manager told reporters. "He was known to have lots of quality, which he has kept, but was not very effective in terms of real production and he was a player without a defensive culture. I think he now works very hard for the team.
Mourinho went on to say that with the money Chelsea paid for the winger, and with him having improved drastically since arriving in London, his value on the market would be massive.
"I'm not worried because if his value was around 40 million pounds when Chelsea bought him, if two years later he's twice or three times better than he was when we bought him, I think his value is a crazy value, so Eden on top of that is not a player Chelsea is interesting in selling anyway.
"Our tag is not to sell, plus the crazy amount that he can value in this moment, I think no chance that Eden can leave."
Hazard has notched eight goals (one shy of his total of nine last season) and eight assists from the wide left position in his 20 Premier League games so far this campaign, yet Mourinho looked to ease the pressure on the former Lille man.
"When we work the way we work, when the players know exactly what they have to do, it's easy for them and he is doing that," he added.
"I cannot expect him to be the match winner every game because it is not fair to put that kind of pressure, especially on a player who comes in from the side and sometimes finds himself far away from the decision area, but we are very happy with him."
Chelsea sits third in the Premier League, trailing league leading Arsenal by two points, and the former Madrid boss says Hazard is relishing the added pressure of the title race.
"He likes the responsibility and feels it is important that we are close to the title. It's a different pressure," Mourinho stated. "If we are 20 points behind Arsenal and he scores three goals it means nothing. If we are one or two points behind and he scores the winning goal in a victory that pushes us to the top, that means something. This experience is good for him."