Can they legally fire him? (My husband had a surgery)

My husband has had surgery once on his left shoulder and twice on his right. When he first started his current job 3-4 years ago he re-injured his right shoulder filling in for a co-worker in an area that was not his normal job. This lead to the second surgery on his right shoulder. They told him if he was not able to perform his job duties in 6 weeks they would fire him. He returned to work and has been performing his duties fine since. Workman's comp did not pay b/c they said it was a "pre-existing" condition.

Recently, he was rammed by another co-worker, on the job, in his right shoulder (twice operated on). He has been in constant pain in his shoulder, neck, and back since then. His boss told him to go to the doctor, but that he may be seen as a "liability" if he cannot "handle a little bump" as he says with this job you sometimes get "bumps" implying that he may be fired. The co-worker himself told the boss it was no little "bump", that he rammed him hard, and that my husband took a hard lick in his shoulder. We want to know if they can legally fire him for this or not if he has to take off work for more surgery or physical therapy or whatever may happen?? He was fine and pain-free until he got hit.

[AFFA]

I wish to inform you that while your husband is on leave because of his injury at work place then he may not be terminated. In case he gets terminated then he may file a complaint with EEOC. In this your husband will have to show that he was injured at work place and may be required to show necessary medical evidence that injury resulted at work place is causing pain and requires treatment. Further, he can also contact the office of the Department of Labor in your state.

AFF

He is not actually on leave yet....he has not even gone to the doctor b/c he was told that workman's comp will probably view it as pre-existing and not cover it b/c he has scar tissue etc. from the previous surgeries. It is getting to the point that he will have to go though, b/c he cannot tolerate the pain much longer.