I don't think his reduced form is anything to do with motivation or decreased effortin fairness Lamela has not played anywhere near the standard of last season. Needs a rocket from Poch.
Therefore I don't think a rocket is going to achieve anything
Perhaps he's fatigued mentally or physically and requires some active rest
Perhaps he's just sufferring from a lack of movement from his team mates and finding it hard to play those incisive passes that he plays so well when at his best