Well if he's replacing Nelson I wouldn't assume there's much difference if comparing who is the quicker of these two. Nelson isn't Usain Bolt by any means.The question is, Is he a speedster (like Jetta) or just avg pace for an afl footballer with really good agility making him look quicker than what he is to dumb asses. Not saying you think one way or the other thats just the question thats been asked and no it doesn't mean he is slow just not a speedster.
I would say Shep and Jetta would be the two quickest in the back line.
In the center line the only pace we have is Shuey and Yeo. Gaff and Masto are good endurance runners.
In the forward line without Ryan and DV we lack pace. Hence I say we need Petrol-celle there to make up for lack of pace in the Forward half. Cripps Lecras Kennedy and Darling are no slouches but not speed demons.
By adding Petrol and Jetta at least we have some pace in all three lines.