What you need to do is to cut back the carpet to the good area. Lay new vino in the void. Attach a new carpet strip, fasten the carpet to the nails, then cover the area with the rolled hood. This should work.
What has probably happened is: this is where the mop hits the carpet and water has built up over time and caused the roting of the carpet. After doing this, be careful with the overlap moping on the carpet.