Keegan is confident the European champions can turn things around at the Liberty Stadium, with in-form Ba leading the charge.
He told The Sun: "Providing Rafa Benitez doesn't mess around with the side too much, I think they've got the quality to win.
"He's got to play his best players in a tournament which could, if we're honest, represent their best chance of winning something this season. They can't win the league now as they're too far behind.
"If you asked the Chelsea fans, I think they'd definitely prefer to see Ba start up front.
"And for me, Ba seems to have a little more life and threat in him than Torres.
"Chelsea are incredibly good away at the moment and Swansea have maybe struggled a little bit at home to get wins this season. We're getting a new brand of football now where some teams are actually enjoying playing away from home more. Whether it's less pressure or it just suits their way of playing, I don't know.
"The tie is definitely in the balance but I see Chelsea just coming through."