The Jameel McKay experiment has not worked. Perth needed McKay to be an explosive scorer, making opposition teams worry about how they were going to defend such a mobile big guy, opening the paint for their slashers, and thus freeing up outside shooters for easy shots. They were relying on Wagstaff to be the shooter he has been in the past, not the one he is now. I don't know what they were expecting from Hire, because I've never seen anything in him. I doubt they were expecting much from Redhage other than an experienced old hand who could keep everyone calm and fill a roster spot for very little money.
The fact that Knight has been injured so much of the season, while it shouldn't be a surprise, has meant that the 'Cats front line hasn't had the meat and potatoes that McKay was never going to provide, and Brandt hasn't stepped up. I'm not surprised about that, either. He's always appeared to be a stiff, to me.
JJ might not have been as big a bust as he appears if McKay had been the threat they hoped he would be. Having said that, Perth can only afford to drop JJ (not McKay) if they are going to make a player move (unless they offload them both, which I cannot see them doing!) The only reason they would drop JJ is if there was a ball-handling, shooting PG available immediately. Cedric Jackson is not that guy. He would need to be able to play 2 when Martin gets back to make it worthwhile.
I think Perth will slide one stop further down the ladder by the end of the season and finish 6th. It will be a shame, if that happens, but successful franchises almost always suffer a slide, and Perth's run of injuries, combined with poor recruiting, is the perfect storm for a fall from finals grace.