A letter grade is obviously subjective, but I think the biggest knocks on him so far have been:
- Riding the starters in the first half with very few off days, which has lead to fatigue and overall offensive slumping in the second half
- Stubbornly sticking with his batting order despite a pile of data showing some hitters doing better in different slots
- Leaving his starters in a batter or two too long when they're showing signs of struggling