The England number one has been a more reliable figure in the Citizens net following his recall to the side, from which he was dropped earlier in the season.
"He has improved a lot," manager Pellegrini told reporters. "It was very important for him to have a rest. Now you can see good performances and that is very important for the team.
"He's improved everything. He was not taking good decisions, maybe his stats were not 100%, so having a rest was very useful to him. I trust him because I see him working every day."
Hart has kept two clean sheets in seven Premier League games since displacing Costel Pantilimon.