It won't take a month, but if you are attempting to improve a player to the point where he caps before he runs out of time to train (most players run out of meaningful time to train at around age 25-26 minus NT players), then your weekly performance is less important that the pops will be for future performance.
Also, keep in mind that defensively speaking you can avoid some problems by swapping positions for defensive setup. So if you have any gimme matchups (you may not), you can still potentially win those with an inefficient offense and a very solid defensive setup.