For several years, Mitch Keller was the face of the Pittsburgh Pirates' rotation and their de facto ace. But the Pirates no longer need Keller; they simply benefit from him. That distinction matters.
For once, the Pirates have built a legitimate surplus on the mound with arms like Paul Skenes, Jared Jones, Johan Oviedo, Bubba Chandler and Braxton Ashcraft comprising the core of their rotation. With Skenes emerging as a true ace and multiple cost-controlled arms coming behind him, Keller’s innings are replaceable.
His trade value, however, may never be higher. That combination – replaceable production with irreplaceable market value – is what makes Keller expendable and heightens the urgency for the Pirates to trade him before it's too late.