Crofts grabbed two second-half goals, either side of Ched Evans' strike for the Blades, as the Canaries bounced back from a below-par first-half showing to claim three points at Bramall Lane.
The former Brighton midfielder now has six goals to his name this season and a delighted Lambert said: "He's created a niche for himself. I think he's one of the best midfielders in the league.
"His all-round game is top-class. I could be biased and every manager will have their own perception of each individual, but in my view he is becoming a really, really top footballer."
Norwich have enjoyed an impressive return to the Championship following their promotion last season and Crofts is one of a number of players to have successfully stepped up from the lower league.
Lambert added: "Most of the lads are untried at this level, but my God they are taking to it brilliantly. You look at the lads I've taken, they've got great hunger and they deserve every bit of credit that comes their way. It's incredible what we have done from where we have come from. In the second half we were excellent."
Source: PA
Source: PA