Of course. Managers dont turn 60 win teams into 90 win teams. Or vice versa.
Talent level ultimately matters most.
But I believe managers have the biggest single influence on whether a team under or over achieves that talent level. Not just "marginal" either.
Turning an 85 win team into a 92 win team, or a 78 win team, seems to me totally reasonable.
I would say Baldelli has been at least that bad. Lots of little things add up.