Sri Lanka's Nuwan Kulasekara believes his discovery of the outswinger has helped make him a different bowler.

He believes that was one of the reasons for his success on day one of the second Test against Pakistan in Colombo.

Kulasekara took four for 21 as Pakistan, who had chosen to bat first, were bowled out for a paltry 90.

Elevated to Sri Lanka's strike bowler following Lasith Malinga's injury and Chaminda Vaas' loss of form, Kulasekara took three wickets in a fiery new-ball spell.

Pakistan never recovered, and Sri Lanka cemented their advantageous position by ending the day on 164 for three.

"I normally like to bowl in-swingers to right handed batsmen. That's my natural delivery," said Kulasekara.

"But I've achieved a lot of success ever since I learnt to straighten the ball and swing it away.

"I haven't tried too many variations such as the yorkers and the slower delivery in Tests.

"That's something I do regularly in one-dayers, but I didn't need to experiment too much here.

"Getting wickets in Test cricket is a lot of hard work. But this morning things worked out well."

Kulasekara, the top-ranked bowler in the International Cricket Council's one-day international rankings, added: "My brief was to stick to a good line and length.

"(Captain) Kumar (Sangakkara) had asked me at the start of the day to aim at a little short of the good length.

"For the left-handers, I concentrated on angling the ball across the batsman and to around about first-slip position."

Kulasekara, who had previously taken just nine wickets in his seven Tests, believes he has the bowling coaches to thank for his success.

"I've received a lot of help from the coaching staff, especially the bowling coaches Anusha Samaranayake and Prabath Nissanka," he said.

"They have worked really hard with me, and I'm very thankful for their inputs."