Very quietly, Grant Williams has become one of Boston's key players, in the sense that when he plays well, they usually win, and when he doesn't play well, they usually lose. Here's his playoff game log the last two series:
G1 vs Mil: 8 points (2-6), 4 reb, L (-12)
G2 vs Mil: 21 points (7-14), 5 reb, W (+23)
G3 at Mil: 9 points (2-9), 6 reb, L (-2)
G4 at Mil: 9 points (3-9), 4 reb, W (+8)
G5 vs Mil: 0 points (0-3), 2 reb, L (-3)
G6 at Mil: 2 points (0-3), 5 reb, W (+13)
G7 vs Mil: 27 points (10-22), 6 reb, W (+28)
G1 at Mia: 7 points (2-5), 1 reb, L (-11)
G2 at Mia: 19 points (5-7), 4 reb, W (+25)
It's not a perfect match, but in the games they've won (5 of them), he's scored 78 points (15.6 avg) on 25-56 shooting (.446) with 24 rebounds (4.8 avg). And in the games they've lost (4 of them), he's scored 24 points (6.0 avg) on 6-23 shooting (.261) with 13 rebounds (3.3 avg).
Or look at it this way:
27 points (G7/Mil) - W (+28)
21 points (G2/Mil) - W (+23)
19 points (G2/Mia) - W (+25)
9 points (G4/Mil) - W (+8)
9 points (G3/Mil) - L (-2)
8 points (G1/Mil) - L (-12)
7 points (G1/Mia) - L (-11)
2 points (G6/Mil) - W (+13)
0 points (G5/Mil) - L (-3)
In the games he's scored in double digits, they're 3-0 by an average margin of +25.3. In the games he's scored in single digits, they're 2-4, with an average margin of -1.2.
In the games he's scored 9 or more points, they're 4-1 with an average margin of +16.4. In the games he's scored 8 or fewer, they're 1-3, with an average margin of -3.3.
Or look at it this way:
5-7 (G2/Mia) - W (+25)
7-14 (G2/Mil) - W (+23)
10-22 (G7/Mil) - W (+28)
2-5 (G1/Mia) - L (-11)
3-9 (G4/Mil) - W (+8)
2-6 (G1/Mil) - L (-12)
2-9 (G3/Mil) - L (-2)
0-3 (G6/Mil) - W (+13)
0-3 (G5/Mil) - L (-3)
When he's shot 45% or better, they're 3-0 by an average margin of +25.3. In the games he's shot 40% or lower, they're 2-4, with an average margin of -1.2.
In the games he's shot 40% or better, they're 3-1 by an average margin of +16.3. In the games he's shot less than 40%, they're 2-3, with an average margin of +0.8.
Obviously it's not a perfect correlation, and even if it was, correlation is not necessarily causation. It just seems like (and the numbers mostly support this) when Grant Williams plays well, the team plays well, and when he doesn't, the team struggles. One huge exception to that was the Tatum game in G6 at Milwaukee. Grant wasn't very good but Tatum went absolutely nuclear so it didn't matter. And of course, none of this factors in his defense.