Gretzky was 6'0" and 185lbs which would have made him about average in size relative to his peers. In fact he was about the same size as Dave Lumley. He was also much faster than you suggest. Gagner is more physical, but Gretzky seldom lost a puck battle. But in the end this is neither here nor there because Gretzky had absolutely incredible skill, far more so than Gagner.
The point is not that because of his size and skating Gagner cannot be an effective #2C. It is that many of us feel that the total package is not what it should be to be the #2C on this team, given the others in the top six who would seem to be more destined to be part of the core. Clearly some disagree, but using Gretzky as a comparative does nothing to help your argument.
He is using Gretzky to compare Gagner too ? First you would have to compare our number 1 center to Gretzky ..RNH and Gagner to our number 2 center at that time Messier . Sorry but as much as i like Sam he could not hold Messier jock strap . When teams focus on Gretzky Messier could take over physically , scoring and play a good 2 way game and make others better . Can Sam Gagner do any of these thing ?
If we are going to us Gretzky size as a comparison , then we need to take a look at who was the center behind him .