Players like him are grossly undervalued because what he offers off the pitch and in the dressing room cannot be quantified.
They're crediting him with the jump in overall quality, with a journalist posing this to him (before the Juve game). Lucas, of course, says it's all down to the team, etc. This was apparently the first time since 2002 that a visiting team has come from behind to win at Juventus.
Looking at Lucas's stats, they're good, but we've seen far more dominant games from him statistically. That said, the fans seem to think he was utterly dominant today, so perhaps head and shoulders above the rest in Italy produces different numbers to the same level of performance in England. Oh, and a couple more oft-used adjectives from today: phenomenal, insane.