Ndombele struggled in his first season in London, both in terms of form and fitness, leading to Mourinho to publicly admonish the player’s efforts on live TV.
However, this season, Ndombele is a key player under Mourinho, starting 17 times across all competitions.
Dele, meawhile, has suffered a role reversal. Having initially been trusted by Mourinho, this season has played just 74 minutes of Premier League football to prompt speculation over his future.
Mourinho, talking about Ndombele, says it is the player's responsibility to motivate themselves. They echo the manager’s remarks made earlier this week, when questioned on Dele, about an “unhappy [player] that believes that it’s not his job to fight and to work every minute for the squad and for the club."
Ahead of Sunday's game at Sheffield United, Mourinho told Sky Sports: "I always say, and I've really felt it all through my career, that the big responsibility for good and for bad is [with] the player.
"We don't make miracles. We don't make players when they have no quality and when they have no desire and no discipline and no motivation. So for good or bad, it's always the player's responsibility and we are the ones who can try to help.
"Sometimes they are open for that and other times they are not. When they are not, there is nothing you can do, but when they are open, you feel that motivation to help them.
"When Tanguy arrived here his condition was not good. When I arrived he was getting small injury after small injury which I believe was his responsibility.
"And for him to realise that he had to change, and work in a different way, is to his credit. Yes, he is playing and playing well. We are happy with him. But, I repeat, it's total credit to Tanguy."