If the pain is on the side of the hip (and not in the groin), then the diagnosis is probably correct (its difficult to diagnose without seeing a patient) but trochanteric bursitis is common and the symptoms match the diagnosis.
Though steroid injections and medications are used to control the symptoms, the mainstay of treatment is physical therapy. It's very common in athletes, not to stretch enough, because they think that sports would provide all the necessary physical therapy. However, certain tissues need to be stretched with particular attention to specific group of muscles.
For trochanteric bursitis, he needs to stretch iliotibial band, which is a band of tissue (like a sheet) that starts from his pelvis, goes on the side of his thigh and attaches below the knee. There are particular ways of stretching it. He may need to undergo formal physical therapy to learn these stretches, and then he can do it at home. I would encourage stretching in the morning and evening for at least a few months.