Pace sensation Naseem Shah grows from cub to lion.

On Monday, Naseem grabbed 5-31 in Pakistan's series-clinching win over Sri Lanka in Karachi to become the youngest fast bowler at 16 years 307 days to achieve the feat.

He broke the record of Mohammad Amir, who made his mark with his first five-wicket haul at 17 years 257 days against Australia in Melbourne 10 years ago.

Naseem's feat has prompted the cricket world to take notice of the precocious ability.

Belief in his talent, Naseem says, has been the key.

"I had belief in my hard work and talent so when I got the chance I tried my best," said Naseem. "I am elated that my feat on a home ground and before my own people has contributed in the win.

I know this is just the beginning and if I keep up the hard work more rewards will come my way.

Naseem Shah poses for a photograph as he kisses a ball for taking five wickets after winning the second Test cricket match between Pakistan and Sri Lanka at the National Cricket Stadium in Karachi on December 23, 2019. - AFP

Naseem's landmark moment capped a three-month fast track progress from a precocious talent to one of the leaders of Pakistan's bowling attack.

He has been in the limelight for some time but it was in October this year that national selectors decided to throw him in the deep when he took nine wickets in a domestic match.

Four days later he was on the plane to Australia for the two-match Test series, a move described as 'throwing a cub before the wolves'. Pakistan's bowling coach Waqar Younis - himself a lethal fast bowler - likened Naseem to former Australian great paceman Dennis Lillee.

"He's got a very strong action. He reminds me of Dennis Lillee actually. He's got a very similar action," Waqar said before the first Test in Brisbane.

He's not as big as Dennis - Dennis was a big guy - but when he gets it right, he's a handful. He's very talented with his pace the key.

Naseem made people take notice with his short burst of eight overs against Australia A, claiming Marcus Harris's wicket with a sharp bouncer.

That was after he received...