Sejanus clearly doesn’t care about winning. Doing the right thing is far more important to him, and Coriolanus realizes this. But Coriolanus doesn’t admire this in Sejanus, necessarily. Rather, he sees Sejanus as a person who will be easy to manipulate and use to make himself look better. So Coriolanus is still interested in winning. But now, he realizes that his win will be even sweeter if he not only wins with a long-shot tribute, but also gets to lord his power over someone like Sejanus, whom Coriolanus doesn’t like.