Tharindu Kaushal, wiry, 22 and tightly wound, charges at the crease, knees climbing, arms drawn briskly up, body like a loaded spring. When his left foot lands, it pivots quickly. His hips wring around, then his wrists. The ball emerges a blur, seam scrambled, whirring when it's tossed up. His is almost a violent action. It sometimes gets violent results.

Rangana Herath, now greying at the temples, stands at the top of his mark, fingers twitching, the ball flitting between hands. His legs begin to move like the wheels of an old steam train. There's an amble, then a shuffle, then a delicate jog. When he gets side-on he slowly turns his belly towards the batsman, like a planet rotating to face the sun. He releases the ball, and you can watch the tilted seam go around, drifting all the way down the pitch. It is gentleness in motion. A cool breeze.

They are both spin bowlers by trade, but on Friday they may as well have been from different galaxies. Herath immediately had the measure of the slow, turning surface. He pushed continuously at batsmen, who rarely had the patience for the game he was playing.

Kaushal cut a desperate figure at the other end. He was so eager, he was too quick through the air. He strained so hard for a little extra bite that in one over, he overstepped four times. No spinner had delivered that many no-balls in an over since 2002. Herath was almost massaging the pitch - in search of a sweet spot or two that might do something for him. Kaushal was shaking the surface for all it was worth.

It is an intriguing duality. Kaushal, it is hoped, will play a leading role in Sri Lanka's future. When he had his doosra banned two weeks ago, the board and coaches rallied quickly around him. The captain expressed in him enduring faith. In a domestic setup that increasingly proves itself to be outdated, Kaushal has been one of the few truly exciting finds. There is a certain messianic expectation attached. If Kaushal is not the next great Sri Lankan spinner, then who?

Herath is Sri Lanka's messiah-by-accident. Six years after picking up Kumar Sangakkara's phone call in northern England, he has a trove of match-winning efforts behind him, and finds himself approaching 300 Test wickets. He didn't have to toil long to get five wickets closer to that milestone on Friday. Some days Herath works on batsmen for several overs - even spells - setting traps, weaving webs. Against West Indies, all he has had to do is vary his pace and turn. Some slid on and hit the pad in front of the stumps. Others turned to clip the edge of the bat or the stumps.

He has embarrassed many a top order here: England and New Zealand in 2012, Pakistan in 2014, India in August. Until today, West Indies had been the only team he has played against that had denied him a five-for.

As time rolls on, perhaps Kaushal will grow a little more like Herath. Age has a way of making people comfortable in their own skin. A few Tests more and Kaushal might not feel like he has to prove himself with every delivery. He is ripping every ball as furiously as he can now, much as his idol Muttiah Muralitharan did at the beginning of his career. But even the bent-armed, noodle-wristed one eventually learned the benefits of subtlety.

Angelo Mathews, for his part, managed Kaushal thoughtfully in the first innings. He took him out of the attack when top order batsmen began to rattle him, then brought Kaushal on again to the tail-enders, against whom he settled. As is often the case with aggressive spinners, Kaushal was a transformed bowler after he had taken his first wicket.

Old man Herath's light flickers now. His fingers still have their magic, but his body, he says, is giving up. Could this be his last outing in Galle? In a year's time, Kaushal may find himself leading the spin attack. Who better to learn from, in the interim, than Herath?