My lazy half suggests that we should probably agree to disagree right here because our opinions are so different, but I'll respond anyway.
Milan's surge was a big deal precisely because it doesn't happen very often. You don't see teams make up 11 points with half the league to go. And that's just considering league positions/points – right now we're on a downward trend, so the gap only looks like it'll increase.
Am I saying we should just give up completely? No, that would be pretty silly, but it's also silly to give away a long-term investment (Mbaye) and a significant sum of cash when our coach's long-term tenure is uncertain and our management could be sacked within a couple months. And all that for a 29-year-old player.
I wouldn't mind a big outlay on Hernanes if we had a more complete squad, but with the limited funds and not-so-great squad we have, we should be focusing what little money we have (or that Thohir is willing to spend) on players who will start and be here for a while. I don't think Hernanes is a guarantee of that.
Big surges don't always happen, I was just saying that they happen often enough, especially that we're at the halfway point and have a lot of games to play. I brought up Milan because I think it's a comparable situation, play like crap, make useful signings, surge. Ultimately, I was responding to all the "The season's over, why bother" posts, of which there are many.
As for giving up Mbaye, it's fair to say that Hernanes would have no resale value and that we'd be giving up a player that can do pretty well for us in the long term. However, my view is, even if Hernanes is only here for a short while and we don't make money off of him, the benefit he'd give our squad now would make up for it. Higher league finish and a place in Europe=more money, we play well=we can attract our targets (how often do players publicly reject us these days?), and a sign of ambition would help us significantly. In my opinion, making use of that immediate positive impact will, in the long run, do us more good than any player's longevity.
Plus, our youth system isn't going to stop churning out RBs. In 2 years' time or whenever Mbaye would actually have a shot, we'll probably be talking about another player.
So yeah, if Hernanes is the only player we can get/the player that our coach strongly believes will make us play well again, then giving up someone that may or may not be in our starting 11 a few years from now seems a small price to pay.