Not necessarily. I don't think the coaches, nor I or many others consider Kersten a key position forward, it was tough for him last year trying to play CHF at 191cm. Walker on the other hand is a genuine key position player and I cannot see all three playing on the forward line, while there are also two ruckmen and three KPD+Mackie, way top heavy. It has been said a few times 'wouldn't it be great if Clarke could hold a ruck spot while Walker teams with Hawkins' and I concur, but I do not think it will happen in Round 1.Two of the NAB cup games featured Hawkins, Clark and Kersten. So they were definitely trialling three big forwards. Kersten wasn't bringing anything to the table and was send back to VFL - but it does show that the MC are looking at this option as their Plan A (trialling it twice in a row). So an in form Kersten would have kept his spot in that forward line. Obviously Kersten and Walker are different - but they are not too different.
Walker doesn't have to push past Mitch Clark. He just has to take Kersten's spot - and do the role the Kersten was expected to do.