The winner will go through to the - on paper - easier group which contains New Zealand, Pakistan and South Africa.
Hosts India, world champions Australia and England await the losers and both captains say they are desperate to win.
Sri Lanka recalled seamer Chaminda Vaas for Ruchira Perera, while Fidel Edwards and Dwayne Smith replaced pacemen Ian Bradshaw and Jerome Taylor for Windies.
Windies suffer early blow: Windies suffered early blow when they lost their batting mainstay Chris Gayle in the very first over edging a regulation catch to Sangakkara off Chaminda Vaas.
Ramnaresh Sarawan soon joined him in the pavilion when he was trapped plumb infront for nought off Vaas. And as though this was not enough, Windies lost its third wicket in the form of struggling Chanderpaul who edged Malinga to the wicket keeper Sangakkara to do the rest, leaving Windies at 17/3 in 7 overs with Skipper Lara (2) and Hinds (1)were at the crease
Sri Lanka: Mahela Jayawardene (capt), Kumar Sangakkara, Sanath Jayasuriya, Marvan Atapattu, Upul Tharanga, Tillkaratne Dilshan, Farveez Maharoof, Chaminda Vaas, Dilhara Fernando, Lasith Malinga, Muttiah Muralitharan.
West Indies: Brian Lara (capt), Ramnaresh Sarwan, Chris Gayle, Shivnarine Chanderpaul, Dwayne Bravo, Dwayne Smith, Carlton Baugh, Corey Collymore, Fidel Edwards, Marlon Samuels, Wavell Hinds.
Umpires: Asad Rauf (PAK) and Rudi Koertzen (RSA)
TV umpire: Mark Benson (ENG)
Match referee: Mike Procter (RSA)