The 16-year-old Dutch defender became the third youngest player in Liverpool's history when he came off the bench in this week's FA Cup tie with Wolves.
Critchley told the Liverpool Echo: "You don't get many 16-year-old defenders playing against Premier League opposition.
“You've got to give massive credit to the manager for having the courage to throw him in.
“Ki had been training at Melwood for a couple of weeks so that will have helped him. He gave a good account of himself. He knows this is just a start and he'll stay grounded."