Welegedara was a late starter to cricket. He learnt to play the game for St. Thomas' College in Matale at the age of 17, but he made rapid progress performing in provincial matches. When he came to Colombo he was selected as one of 15 probables by Daryl Foster, the Australian fast bowling coach, for the Sri Lanka Pace Academy headed by former Sri Lanka fast bowler Rumesh Ratnayake in 2000. Soon afterwards he was sent to the MRF Pace Academy in Chennai to further develop his skills. Playing for Moors SC since 2002 he bowled his club to the Premier league title in 2002-03 capturing 34 wickets (avg. 24.14) in 13 matches. But his career-best performance came the following season when he took a match haul of nine wickets against Colombo Cricket Club to steer Moors to a comprehensive ten-wicket win. He took the majority of his wickets bowling inswing and trapping the batsmen leg before. Welegedera toured Sharjah with the Sri Lanka Academy side and took seven wickets against UAE, which earned him selection for Sri Lanka A. But he suffered an ankle injury and had to be operated in Australia. The injury kept him out of cricket for 1 ½ years, but his Test debut finally arrived against England, in Galle, during the 2007-08 series. He impressed with a strong action and brisk pace, marking him out as an ideal successor to Chaminda Vaas.