Cracked for 27 runs in his first over of the tournament, having returned to claim 4 for 27 against the same team eight days later, Shardul Thakur has now returned the Nidahas Trophy's best figures, as well as its most expensive over.

He says he doesn't mind a challenge. On Monday's evidence there is little reason to doubt him. Varying his bowling on what was an excellent batting track, Thakur was instrumental to wounding a Sri Lanka innings that was threatening a score in the vicinity of 180. They wound up only making 152 for 9 off their 19 overs.

Thakur's is the latest performance which outlines the depth in India's ranks. In this tournament they are missing Jasprit Bumrah, Bhuvneshwar Kumar and Hardik Pandya, but in Thakur they still found a bowling match-winner. He is used to filling the shoes of better reputed bowlers.

"I have told one thing before: I love challenges," Thakur said. "I am taking it as a challenge. If other senior bowlers are missing from the team, then I have to step up. I have done this previously for other teams that I have played for. I have come in place of Zaheer Khan, Dhawal Kulkarni and Ajit Agarkar while playing for Mumbai. I had to step up in that role. When senior bowlers are rested, I have to step up and fill that role to lead the pace attack."

That leadership, in part, was set off by his cunning. Sri Lanka were flying at 113 for 3 in the 12th over, when Thakur slipped in a special delivery. His knuckle ball, which is delivered without the two fingers behind the seam, dipped a little earlier than batsman Thisara Perera expected, and came a little slower as well. Attempting to blast it over the long-on boundary, Perera could only send it high in the air, to be eventually caught at cover. Then, in the final over, having expected Dasun Shanaka to come down the pitch, another Thakur knuckle ball collected the outside edge of the flashing bat, and was caught by the keeper.

It is a ball that has been used by India bowlers before - specifically by Zaheer Khan, who had more or less pioneered it in the IPL, and also by Bhuvneshwar Kumar.

"[Zaheer] did it actually, but I didn't watch much of his videos," Thakur said. "I always knew what the grip was, and then I learned it on my own.

"I've been practicing it for a long time. It hasn't come easy. Whenever I found time to play with white ball while playing domestic cricket, I used to try knuckle ball. Probably for two years I've been practicing it now."

Having taken 1 for 25 in the previous game against Bangladesh, Thakur and his knuckle ball have helped India restrict oppositions to sub-par totals in consecutive matches now. By Thakur's estimation, Sri Lanka were about 25 runs short on this pitch.

"If you see, in T20 cricket, you have to be ready for surprises. The first game was a surprise and an eye-opener for us. I got hit for 27 runs, there were some other overs that went for 15 runs. But I felt that the game against Bangladesh and this game, we executed our plans better."

India will confirm their place in the final if they win on Wednesday, but have a chance to go through even if they lose, based on net run rate.

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