Right back and left back are pivotal to the way we play. Baines and Coleman give us massive attacking options which is why Barry and McCarthy play deep, covering their runs.
When Baines was out last season, Oviedo dropped perfectly into the system. We don't have a natural replacement at right-back which fits the system so we struggle when Seamus is out. Given we don't have a bottomless pit of money to have a replacement attacking right back sat on the bench or just in the squad, it's down to Martinez to find some sort of compromise. So far he hasn't really managed to do that.
Hopefully Seamus will be fit for most of the season and we won't get punished too much for it, but i'd say if we're going to have Stones or Hibbert at right-back then we need to be pragmatic about it and don't push them on so much trying to do what Seamus does so brilliantly. If Barkley was fit there might be something for him playing centre midfield with either Barry or McCarthy ( probably Barry if Baines is going to bomb on ) doing the holding role on their own.