The French youngster burst onto the scene at Blackburn in 2009/10 with a string of impressive performances.
He has, however, stagnated somewhat since then and has slipped down the Ewood Park pecking order as a result.
Phil Jones and Vince Grella are currently ahead of him in the battle to secure a midfield berth, with both having made steady starts to the new season.
Allardyce feels N'Zonzi is not doing enough at present to force his way into the fold and has warned the 21-year-old that he needs to knuckle down if he is to fulfil his undoubted potential.
He said: "Steven N'Zonzi? I don't think he has been unlucky, I just don't think he has played to the level he played last year.
"That is the reason he hasn't been in the side.
"Vinny, who struggled last year because of injuries, has kept himself a bit fitter and is getting in the frame a little bit more.
"That puts pressure on Steven. He has got a kick up the backside."