The landlord can't make a claim under an imaginary warranty - either there was a warranty or there was not - and as he's claiming damage beyond ordinary wear and tear that's not something a carpet warranty would cover. Also, if we assume the warranty was the same, you have given us no indication that you professionally cleaned the carpet at any point during your two-year tenancy.
If the full replacement cost was $1,200, the landlord's claim for damages would be for [(expected life of carpet - 2 years) / expected life of carpet) x $1,200].Quoting spence0021
You can argue to your landlord that this was ordinary wear and tear for which you were not responsible. If you cannot convince your landlord of that, or come to a mutually acceptable resolution, you can file a lawsuit to try to recover money from your landlord based on your assertion that this was ordinary wear and tear and not damage.

