I actually think Nene has been alright, he's been doing all you can ask, he has a few issues defensively, but hoffs are worse.
I would probably think about swapping Hoff for Davis. I really liked Davis and i would be more than happy to have him back. I would move Mead back to Fullback and Zillman out to Meads wing. I'd drop Don, he hasn't been playing anywhere near his potential for the last 5ish weeks and he is most likely to not be resigned at the end of this season, i reckon it's time to pull the trigger and give BK/GL/Olive/TRD a go and see what they can make of it.
Looking into the next few years, backline should be something like
1. Mead
2. Olive
3. Mcdonald
4. Davis
5. BK
and then later down the track something like
1. GL
2. Olive/TRD
3. McDonald
4. Davis
5. BK
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he's most likely only picked to justify his pricetag, remember reading somewhere he turned down a 700k offer from canberra to come to us, pretty worrying what he is on if it's true