I am a Kelsay hater as well, however last season, I too noticed his marked improvement in the 2nd half of the season (especially the last 4 games). He went from awful to average. Hopefully a full year of this defense he'll go from average to above average, but I will never expect average to good or even great. If he can be an above average OLB, that should be enough... for now. His replacement should already be on the roster, or should be drafted next year.
We don't need studs at every position. We need 8 solid players, and 3 studs. Last year, we had 8 weak players, 2 solid players, and 1 stud.