David Luiz continues in central midfield for the Blues while Michu leads the line for Michael Laudrup's side in a rematch of this season's Capital One Cup semi-final
Frank Lampard is also sacrificed from the team beat Basel in the Europa League in midweek as Ramires partners his compatriot, David Luiz, in the centre of midfield.
John Terry keeps his place at the back but Gary Cahill plays ahead of Branislav Ivanovic. Behind Ba, Oscar, Juan Mata and Eden Hazard are reunited after only the Belgian started in Switzerland.
Swansea boss Michael Laudrup, meanwhile, opts for a 4-3-3 formation with Michu leading the line in between wingers Wayne Routledge and Pablo Hernandez.
Leon Britton, Ki Sung-Yueng and Jonathan de Guzman line up in midfield, while Michel Vorm is preferred to Gerhard Tremmel in goal.
Chelsea starting XI: Cech; Azpilicueta, Terry, Cahill, Cole; Ramires, Luiz; Oscar, Mata, Hazard; Ba
Subs: Turnbull, Ivanovic, Bertrand, Lampard, Benayoun, Torres, Mikel
Swansea City starting XI: Vorm; Rangel, Flores, Williams, Davies; Britton, Ki, De Guzman; Routledge, Michu, Hernandez
Subs: Tremmel, Monk, Tiendalli, Taylor, Dyer, Moore, Shechter