Mendis sustained a hamstring injury during training on Tuesday (February 24). The International Cricket Council's (ICC) Event Technical Committee has approved Tharanga as his replacement.
According to ICC rules, any injury or illness-based replacement requires a written submission to the Event Technical Committee along with a diagnosis from a medical practitioner as to the extent of the injury or illness. Once replaced, a player may not return to the squad save as an approved subsequent replacement for another injured or ill player.
The Event Technical Committee of World Cup 2015 is Geoff Allardice (ICC General Manager - Cricket, Chairman), Campbell Jamieson (ICC General Manager - Commercial), John Harnden (Chief Executive, CWC 2015 LOC), Gavin Larsen (Cricket Operations Manager, New Zealand), Russel Arnold and Sanjay Manjrekar (independent nominees).
Sri Lanka, who are in Pool A, next face Bangladesh tomorrow (February 26) at Melbourne Cricket Ground. They lost the World Cup opener to New Zealand and in the second match, won against Afghanistan.