Two Ukrainian Krivak frigates would add limited combat power

How much trouble could two former Ukrainian Krivak-class frigates have caused Russia if they had avoided scuttling and returned to active service?

Not much; they were aging frigates with difficult service histories, including use of related ships in coast-guard roles.

Two additional hulls would give Ukraine more patrol and presence capacity, but no decisive answer to the Russian Navy. The ships belonged to an aging frigate family whose later service was not especially successful. Their condition and support requirements would matter as much as their nominal armament. Survival and reactivation would produce a modest improvement rather than a major change in the naval balance.