I'm definitely pointing a finger at Melo in terms of D along with other Vets that didn't get the job done defensively.
First off PG/SG is MUCH harder to defend than SF/PF. Plus a kid like Baker had to learn a new position as a rookie facing the quickest players in the world fighting over screens!!!
Here are the Knicks players rank in the League in Defensive Real Plus Minus:
ESPN
2016-17 Real Plus-MinusRK NAME TEAM GP MPG ORPM DRPM RPM WINS
52 LeBron James, SF CLE 74 37.8 6.49 1.93 8.42 20.43
53 Kristaps Porzingis, PF NY 66 32.8 -0.31 1.90 1.59 6.54
94 Joakim Noah, C NY 46 22.1 -2.23 1.17 -1.06 1.32
97 Kyle O'Quinn, C NY 79 15.6 -1.28 1.16 -0.12 2.31
142 Marshall Plumlee, C NY 21 8.1 -1.75 0.65 -1.10 0.22
173 Willy Hernangomez, C NY 72 18.4 -0.75 0.40 -0.35 2.37
183 Sasha Vujacic, SG NY 42 9.7 -2.35 0.26 -2.09 0.27
188 Justin Holiday, SG NY 82 20.0 -0.58 0.25 -0.33 2.87
264 Maurice Ndour, SF NY 32 10.3 -1.94 -0.37 -2.31 0.07
298 Ron Baker, SG NY 52 16.5 -2.68 -0.56 -3.24 -0.06
359 Mindaugas Kuzminskas, F NY 68 14.9 -0.80 -1.20 -2.00 0.72
379 Chasson Randle, PG NY/PHI 26 11.5 -0.74 -1.36 -2.10 0.20
394 Brandon Jennings, PG NY/WSH 81 22.2 0.25 -1.50 -1.25 2.15
395 Courtney Lee, SG NY 77 31.9 0.58 -1.51 -0.93 3.40
418 Lance Thomas, SF NY 46 21.0 -2.87 -1.73 -4.60 -0.91
421 Carmelo Anthony, SF NY 74 34.3 1.87 -1.75 0.12 5.26
442 Derrick Rose, PG NY 64 32.5 0.11 -2.36 -2.25 1.17
468 Doug McDermott, SF CHI/OKC 66 22.8 -0.61 -3.92 -4.53 -1.33