Grealish has been up there, performance wise.
Haaland has to be the top City player because of his output, simple as.
KDB has been incredibly streaky. He had a torrid run of form that saw him benched for a while (read
Pep's comments). Bernando's head is in Barcelona. Mahrez comes alive when the CL anthem plays but is otherwise a solid rotation option.
City's most consistent and great attacker this season, taking all phases of play into consideration (not just the final assist/goal), and excluding Haaland, is Grealish.
Ake is City's best defender this season. If not for Zinchenko's great season I'd have Ake as the top performing LB in the league.