TV cameras opted not to show full replays of the challenge, taking place in the 77th minute, with the damage caused being too gruesome to broadcast a second time.
Son, who saw red for his part in causing the injury, was visibly distraught, as were a number of other players who saw the challenge close up.
Players from both ranks frantically waved to the medical team, with play being stopped for around eight minutes as the situation was assessed and he was secured to the stretcher.
There is no word as yet as to the exact nature of the injury, with that likely to come out in the next few days once the dust has settled.
Spurs had led 1-0 through Dele Alli's superb strike on the 63rd minute, and would be pegged back by Cenk Tosun's header deep into the 12 minutes of injury-enforced stoppage time, but the football was overshadowed by the seriousness of the injury.
Son's inconsolable reaction was telling of that, the red card given to him by Martin Atkinson feeling like something of an afterthought as he was consoled by manager Mauricio Pochettino, who had made his way onto the park.
The point moves Everton three points clear of Southampton in 17th, while Tottenham remain in the bottom half in 11th, level on points with 10th-placed Manchester United.
Source : 90min