Its not that Tierney needs to be fired off to the sun for no reason or for nothing, but he is not a core player and is going to be paid at his absolute max value for his career because of the timing.
There is no reason to trip over themselves to give him any sort of term or pay market value in a time of a flat cap. Squeeze him to a short term lower value contract like they usually do or say good luck getting that elsewhere, we'll find you a new home. If he were on the open market this year, that 5 million with term would not be available to him from other teams either, at least I'd be shocked if it were.