Just read on cricinfo that Ryan Harris has been told he must get to a point where he can gaurentee that he can play 5 days.
From cricinfo:
"One of the most problematic men among the quintet of players omitted from the Brisbane Tests, Harris, 32, is Australia's best bowler when fit, but seemingly less likely to remain so with each match he plays. Pat Howard, the team performance manager, has decreed Harris must be brought to a point at which he is capable of performing for five days before he can resume with the team."