Spiers will open the season as the Reds' fifth starter, Gordon Wittenmyer of The Cincinnati Enquirer reports.
It could be temporary until Andrew Abbott (shoulder) is ready, but Spiers will have at least a couple starts to convince the Reds he should remain in the rotation. The right-hander has had a strong showing this spring, collecting a 2.70 ERA and 10:4 K:BB across 10 frames.