Dimuth Karunaratne's outstanding run over the past 18 months is down largely to his experience. So said Angelo Mathews, of a batsman he has known since high school. He and Karunaratne played together for St. Joseph's College in Colombo, for a team in which Mathews was the star captain. But Mathews, like everyone else, has been lavishly outscored by Karunaratne in bowler-friendly series.

Karunaratne's aggregate across the two Tests is 356 - 195 runs more than the next highest-scorer. He has also passed 50 in each of his four innings, and is the only centurion so far, having made 158 not out in the first innings in Galle.

"With experience you improve, and you learn from your mistakes," Mathews said. "We all can see that Dimuth is not repeating his mistakes. That is the quality a batsman should have. I have been with him since school. I know him in and out and he is a strong character. He doesn't easily give up."

Although Karunaratne was an inconsistent performer in the first few years of his career, he has seemingly matured into a more reliably run-producer since the start of 2017. He had scored over 1000 runs in the last calendar year, in which he hit centuries against Bangladesh and India, as well as making 196 against Pakistan in Abu Dhabi - an innings that set up victory in that game. Now, in 2018, he averages 65.15 after four Tests.

"The way he has batted in the last year or so has been brilliant," Mathews said. "He was outstanding in UAE when he got those huge runs in both games. Once again, here, he showed that on difficult wickets he can score runs. If you all recall, on a difficult wicket against India at the SSC last year, he scored a hundred as well. He has added a lot of stability into our line-up."

What Karunaratne has done well on the spin-friendly pitches in this series, is search out scoring opportunities, Mathews said. "You always can get a good ball on these wickets. You can't wait for the good ball. On these tracks, you've got to score runs, and keep rotating the strike so that it gets easier. That's what Dimuth has done."

Although Karunaratne has helped set up the series whitewash, Sri Lanka require five more wickets to close out the second Test.

"Beating the No. 2 team in the world is something special, and it's going to be a huge achievement for us as we're an inexperienced side," Mathews said. "We will enjoy that. But we have a job at hand tomorrow morning. The first couple of wickets are going to be crucial. If we can knock off a couple early then we can enjoy the victory."

Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @andrewffernando