They showed him hitting the practice field. I'd imagine this is one of those things that's super deadly if it sneaks up on you but manageable once you've identified it? I really don't know. Trey Smith seems to be doing just fine though.
typically the management of a hypercoagulable disorder (propensity to develop clots) after you've already developed a clot is anticoagulation (blood thinners) for life. he wouldn't be able to play a contact sport like football as it would mean he would be at high risk to bleed anywhere, with the most feared being a brain bleed due to the nature of the sport.
if he has a hypercoagulable disorder and he decides against blood thinners in order to play football, this means he would be at high risk to clot again. the pulmonary embolism he developed could have killed him and if truly hypercoagulable, he would be at risk for something like this again.
it's good to hear he is on the field but i imagine we won't ever know the fine details regarding his diagnosis or what discussions went on in the background when he decided to play. i hope he takes care of himself and everything turns out fine.