Have to assume a solid + from CHI or heavy retention, otherwise I have no idea why the oilers do this. 5.5 in a flat cap could get you a lot of far better Dmen than 38 YO Duncan Keith.
Most reports have Chicago absolutely unwilling to retain.
If that's true, and what's going back isn't James Neal, this trade is a loss for the Oilers almost regardless of what else is going back. Adding Keith at 5.5 severely hampers our ability to improve in places we actually need to improve, which is in goal and top 6 forwards.
If the immediate take from the team's beat writer is "hot damn, money for a better defenceman" I have serious concerns.