There is nothing Doc or Pop could have done to make KG produce much better than he showed this season. KG is not at Duncan's level of play he's got too many miles on his body. Age.
Last game he grabbed 12 boards, dished 3 assists and had 3 steals in less than 21 minutes.
In game 7 against the Raptors he grabbed 11 boards and scored 13 points in only 25 minutes.
In fact, in the only games in this playoffs where he's played at least 25 minutes he's averaging 12.5 points on 67% FG in 26 minutes.
KG '13: 12.7 ppg, 13.7 rpg, 0.8 spg, 1.0 bpg, 3.2 TO
KG '14: 7.0 ppg, 6.0 rpg, 0.9 spg, 0.6 spg, 1.0 TO
But now, let's look at it per 36 minutes:
KG '13: 12.9 pts, 13.9 reb, 0.8 stl, 1.0 blks, 3.2 TO
KG '14: 12.8 pts, 11.0 reb, 1.6 stl, 1.0 blk, 1.8 TO
Why not give him 30 - 35 minutes a game from here on out? If he's done, well, then the team hasn't lost anything because they weren't going to win anyway.