Re integrating rooster

I have 2 brown leghorn roosters that are around 14 weeks old. One is definitely dominant, he is called joe, the other one is bob. A week ago when we let the chickens out in the morning, bob was not with them. We checked the coop and bob was injured, with his foot stuck. I thought he was dead but he moved, so I brought him in the house and took care of his injury. One leg was swollen, but not broken, and in a couple of days he was feeling much better. When I went to put him back with the flock joe chased him and attacked him and Agnes sat on him and pulled his feathers out. He is separated again now. How can we put him back with the flock without them hurting or killing him?