He already had the blood clot in his neck, which was the cause of his pain. The chiropractor's massage released the clot.

Sorry for your friend. It sounds unfortunate all around.

I'm not a doctor but I was an athlete and the default suggestion of "my neck/knee/legs/arms hurt" -> massage is standard common wisdom. Maybe an MD would have stalled for an ultrasound but then you have all of the insurance and delay issues.