That's pretty simplistic. They played different teams, under different circumstances, different injuries...lots of variables. The defense in general played much better towards the end of the season, with him in the lineup, no? He likely wasn't up to speed those first couple games back either.
I'm not a die-hard Byrd fan, but I don't have negative feelings towards him. I hope they work it out, and keep him.
He was okay, but he is a long time vet, so the playing experience wasn't much of a benefit to him. And how exactly did this team, that missed the playoffs, benefit from Jim Leonard getting more playing experience? Are you expecting him to build on this experience, and play even better next year?