Kieboom is a total wild card. He struggled in a cup of coffee last year, but so did Mike Trout famously in his first cup of coffee. That's not to say Kieboom will be Mike Trout, but the Nats do seem to have a solid amount of confidence in him. I think he could have a Robles-level rookie year, where he's a solid starter. That isn't going to replace Rendon, but you have to hope for that difference to be made up elsewhere (bullpen, Robles improving, Turner taking his game to another level with a healthy finer, etc).