His moments of quality are fantastic but I think he's under-acheived versus his skill level. His best club season was 2014/15 with Real, 47 appearances, 17 goals, 18 assists. That's:
A) his best season ever, when true world-class players string several such seasons together;
B) for Real, surrounded by elite talent;
C) not even that impressive all told. Dom had 21 goals last season. Lukaku, 26 and 7 in his best year with us. Even the Scandinavian Voldemort had 41 appearances, 14 goals, 7 assists in his best year with us. That's just three players i looked up off the top of my head, there are better comps out there and there are many of them is my point.
Look at his body of work - he's a good player on excellent sides. Even at his best he was never an indispensable player, those sides would have gone on to league and CL success without him.
I think he's been trading off his 2014 WC success his entire career. That was an achievement but it's a handful of games, it's an anomaly. That, and his charisma and star power.
He never stuck at any club for long.
He didn't have any bidders this window.
Even Carlo didn't want him.
Even Colombia didn't want him.
He was hurt a lot.
He doesn't fit the system, the way we line up his position doesn't exist.
He doesn't do the two-way work that's required in the way we play - if DCL, Richy, Allan, Townsend, and Doucoure are all tracking back and applying pressure, and he's just flitting around and waiting for the ball, sure he may pick out a wonder-pass or put it on a postage stamp once or twice a game, but every possession there's one less man doing that work and it's that much easier for the opposition to get upfield.
Most importantly IMO, by selling him we can spend. The January window is not ideal but better late than never, and if we have a huge amount of cash coming off the books and if we can get 3 dependable heavy rotation players for that money between January and the next summer window I'd be delighted.
Then you add his attitude problems with the manager - fault who you like, but he's in charge now - the way he sulks on Twitch, his private-jet act when we're getting slaughtered at City, etc. -
easy for me. Move him on and get the money.