Looks like Killen and Neilson would play if selected!
"....After forms were sent players who could come into the side under the "three players over 23 rule", former All White captain Ryan Nelsen, now captain of Blackburn Rovers in the English Premier League, and Celtic's Chris Killen made themselves available.Phoenix players Shane Smeltz and Tony Lochhead have also said they would play if selected..."
With the Olympic football having no profile in the UK - there being no GB team - I'm not sure that Blackburn and Celtic would have thought it a possibility that they could lose players for three weeks. It is common for players not go to the youth finals. Though after England were hammered by FIFA for sending an almost completely different team from the one that qualified to one of the youth WCs (Nigeria?) a few years back that may have changed.
Question - do the player release rules apply to the Olympics like they do to senior FIFA tournaments? Do Blackburn and Celtic have a say?