I don't mind keeping him as back up either. However we've effectively got Lucas, Allen and Can who can all be considered back up in that midfield department as of right now. Can obviously has youth on his side, so he deserves some time to show us if he can control a game.
We've also got our 2 captains who are pretty much guaranteed to start. So if we go and sign an improvement on Lucas, for me it's either him or Allen gone. I'd personally prefer it to be Lucas, he's had his shot. He's had some very good games along the way, as well as some awful ones. But he's never been able to do it consistently for more than half a season at most, whether that's down to talent or through his injuries, I don't know. I just know it's time to move on.
Allen is worth a few million, Lucas is worth almost nothing and I think on relatively small wages. I'd sell the one that could make us a few quid. But I wouldn't be too disappointed to see them both moved on.