Blackett joined Celtic on a season-long loan deal from Premier League outfit United in the summer transfer window.
The 21-year-old has struggled to break into the Hoops’ first team, and he started Thursday’s Europa League Group A clash against Molde on the substitutes' bench.
The youngster, though, was thrown into action after just nine minutes when he came on for Jozo Simunovic.
The England Under-21 international struggled against the Norwegian side and was substituted in the 69th minute.
Former Celtic midfielder Lambert watched the game, and he has suggested that he does not think that Blackett is not ready for the Bhoys yet.
"I watched the young lad (Tyler) Blackett the other night - he looked so petrified,” the former Scotland international told BBC Scotland. "Every time he had the ball he looked as if he had a mistake in him. You thought, 'the game is too big for him'.
"It's great being a player at Dundee United, Motherwell or Hibs and you look great, but you throw them into that Old Firm environment and there are 60,000 absolutely demanding that you win a game of football. You've got to be so strong in the head to handle 60,000 criticising you or praising you."
Celtic lost the match against Molde at Celtic Park and are now in danger of not progressing to the knockout stages of the Europa League.
Ronny Deila’s side, though, bounced back from last week’s disappointing in style on Sunday afternoon, defeating Ross County 4-1 away from home at the Global Energy Stadium in the Scottish Premiership.