Unless they could help us in the future and/or increase their fee.
According to Whoscored, Vlasic is the 2nd rated player in the entire league. Since the 2013/14 season - farthest it goes back, I couldn't find anyone even close to that age in the top 5, the closest was Golovin a year or so ago at like 9th. It's borderline unprecedented. We clearly need a backup for Siggy and it's not like Vlasic can't play a couple different positions. He could help us.
Lookman has something to him. With Richy emerging on the right side, Lookman suddenly becomes our backup left sided player, which is his natural position. He put up great numbers at RBL, granted, they play a very different system, but think he'd do well from the left here.
I already noted how Onyenkuru is putting up numbers that few are.
I'm not against selling them, but they've clearly got potential. It wouldn't be for some small fee, that's for sure.