Spinners Maheesh Theekshana and Wanindu Hasaranga set up a comprehensive seven-wicket win for Sri Lanka against debutants Namibia in round one of the Twenty20 World Cup on Monday.
Theekshana returned figures of 3-25 and Hasaranga took two wickets to help dismiss Namibia for 96 in the second Group A encounter of the day in Abu Dhabi.
The left-handed Rajapaksa, who survived a dropped catch on 18, smashed four fours and two sixes in his 27-ball blitz.
But bowlers remained key to victory with quick Lahiru Kumara also chipping in with two wickets to bowl out Namibia in 19.3 overs after Sri Lanka chose to field first.
Craig Williams with his 29, skipper Gerhard Erasmus, 20, and JJ Smit, unbeaten on 12, were the only three batsmen to manage double figures.
Sri Lanka, champions in the 2014 edition, top the group table ahead of Ireland, who thrashed Netherlands by seven wickets in the first match that witnessed Curtis Campher taking four wickets in four balls.