Unfortunately, due to a mix-up, I wasn't passing the homography, and in debug, the matrix was composed of 9 times 0...
The problem has been fixed, and now the projection of the players onto the pitch in the view has completely changed.
Below are the logs of the pitch points and the mapped points, and the log of the player position calculation.
soccer field point : [NSPoint: {0, 0}, NSPoint: {0, 0.20319999999999999}, NSPoint: {0, 0.63470000000000004}, NSPoint: {0.15709999999999999, 0.79669999999999996}, NSPoint: {0.15709999999999999, 0.20319999999999999}]
mapped point : [NSPoint: {0.71256458040024129, 0.33116703539823011}, NSPoint: {0.56118128708266291, 0.37885911102172165}, NSPoint: {0.070450381511464197, 0.52026347546259055}, NSPoint: {0.24582505782381334, 0.70927192276749795}, NSPoint: {0.91810702433628322, 0.42165501810136768}]
players position
Player 1 position (751.25, 343.4765625)
Player 1 normalized position (0.5869140625, 0.47705078125)
Player 1 homographic point (0.10142949595301291, 0.4261338885074528)
Player 1 scaled position (40.57179838120516, 110.36867712343027)
Player 11 position (547.1875, 269.6044921875)
Player 11 normalized position (0.427490234375, 0.37445068359375)
Player 11 homographic point (-0.04883335365913332, 0.24101459684534468)
Player 11 scaled position (-19.53334146365333, 62.42278058294427)
Player 7 position (820.625, 315.85693359375)
Player 7 normalized position (0.64111328125, 0.438690185546875)
Player 7 homographic point (0.08648478109704534, 0.3313839741406798)
Player 7 scaled position (34.59391243881814, 85.82844930243607)
Player 2 position (798.125, 354.55078125)
Player 2 normalized position (0.62353515625, 0.492431640625)
Player 2 homographic point (0.12250871101443257, 0.44441790211234544)
Player 2 scaled position (49.00348440577303, 115.10423664709747)
Player 4 position (718.75, 235.1513671875)
Player 4 normalized position (0.5615234375, 0.32659912109375)
Player 4 homographic point (-0.066713761051341, 0.0376760262301291)
Player 4 scaled position (-26.6855044205364, 9.758090793603436)
Player 12 position (1018.75, 303.3984375)
Player 12 normalized position (0.7958984375, 0.42138671875)
Player 12 homographic point (0.11930564207179961, 0.24230499842427267)
Player 12 scaled position (47.72225682871984, 62.756994591886624)
Player 14 position (1015.625, 396.4306640625)
Player 14 normalized position (0.79345703125, 0.55059814453125)
Player 14 homographic point (0.20022164864096584, 0.4974407454994356)
Player 14 scaled position (80.08865945638634, 128.83715308435382)
Player 16 position (340.625, 371.9091796875)
Player 16 normalized position (0.26611328125, 0.51654052734375)
Player 16 homographic point (0.046689431927868986, 0.5789737221398762)
Player 16 scaled position (18.675772771147596, 149.95419403422792)
Player 3 position (676.875, 260.3759765625)
Player 3 normalized position (0.52880859375, 0.36163330078125)
Player 3 homographic point (-0.030184739272659515, 0.16754098935548395)
Player 3 scaled position (-12.073895709063805, 43.393116243070345)
