I was thinking that too - actually I was sorry he didn't play at Dortmund. Maybe would not have changed anything on the night but seems to me it would have been the better decision.
He also "may not be a natural RB" (TBH I'm not sure what that really means) but he doesn't seem to be out of place there, and being a good defender already it is very likely to assume
he'd improve in that position too with experience. He's 19 (though it is really hard to believe watching him play). This is not easy and I guess it wouldn't be a popular decision, but I'd play him even ahead of Debuchy
(at least when the defensive part is more required - for the bigger game, in general).