"We had a shaky period under Roy Keane when we didn't win for about seven matches which dragged us towards relegation," McCartney said following Saturday 's 0-0 draw at Arsenal.
"But 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.
"Ricky Sbragia's taken over the job and he's give 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 of 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.
"With the players that Roy Keane brought in we were looking to build on what was achieved last season, so the top ten was in our sights and it's pleasing to see us up there now." Sunderland chairman Niall Quinn's decision to appoint Sbragia seems to have been vindicated with his club steadily climbing to Premier League safety.
They were boosted by a point at the Emirates but McCartney felt his side could have stolen a victory.
McCartney added: "In the first half we had a lot of the ball and we tried to catch them on the break. We just didn't have the finished product to find a way past Almunia.
"But it was a good overall performance and after the game the lads were overjoyed in the dressing room. I don't think any side comes to the big teams and wants to sit back and defend for 90 minutes. It certainly wasn't our game plan.
"We wanted to pass it around and create chances. Arsenal weren't firing on all cylinders and we capitalised, and especially first half we passed the ball well and matched them.
"Afterwards the lads were talking about how Arsenal seemed to run out of ideas as the game went on. It was probably one of the easiest times we've ever had coming here.
"For the first 10 or 15 minutes they had us on the back foot and created chances. But as the game went on they didn't come up with much to threaten us.
It was a great team performance from the lads.
"Our keeper has made some good saves and they've had one or two decent opportunities, but every time we had the ball we passed it well and tested their keeper a few times. To be honest, with a bit better finishing, we might have nicked it."