I'm looking at this as well.
I can trade next week to get 18 players while still holding Oliver. If I trade him as well, it replaces my 18th score (a rookie) with a premium. So maybe 120 vs 50 points.
But then in R13 I'll have close to 18 premiums anyway (only Stewart misses), so the 18th score might be more like 80.
So maybe 100-150 points gained by trading him
How much does he outscore his replacement in the last 9 games though?