5000m in a triathlon does in no way represents a 5k race !
in any case if you want to beat jenson button it is hard. this guy i met wrote a 'i think i can beat jenson button' blog and in the end he did not beat jenson button at the triathlon. he was a few seconds out so it is a very good read on how to prepare for a race.
in any case i met this guy and he ran 18 minute 5k parkrun at finsbury parkrun. this is a hard course so you would have to be near 17.30 5000m on a flat course. he lost to jenson in the end so to beat the the champion you might be looking at 17.30 at a stand alone 5k race.
in any case have a read of this. best of luck !
http://ithinkicanbeatjensonbutton.tumblr.com/
Edited: 21/06/2011 at 21:52