Keane left Sunderland in December with Sbragia initially taking over on a caretaker basis before the landing the job on a permanent basis.
McCartney admits all was not well under Keane's stewardship and that the players are far happier and relaxed under Sbragia.
"We had a shaky period under Roy Keane when we didn't win for about seven matches, which dragged us towards relegation," McCartney told the Sunderland Echo.
"But, in the last four or five games under Ricky, we've started playing better football and got more confident with each match we've played - and that showed against Arsenal.
"It's good to be looking above us, rather than below, all the time.
"Having a happy dressing room is always a base to build on.
"If the team spirit's low, then when you go out on to that pitch you're not really going to achieve anything.
Freedom"Ricky's taken over the job and he's given the lads a bit more freedom to express themselves and it's paying dividends in the matches we've played.
"He talks to us more and a player knows that, when he goes on to that pitch, he has to give 100 per cent all the time.
"I think, under Roy Keane, the lads were a bit disheartened and he went about things differently from the way Ricky does.
"He's given the lads self-belief again."