[Ramrod]

It should be possible to carefully manage that type of injury through to a proper resolution. The hamstring injury needs to be assessed (possibly with diagnostic ultrasound imaging) and the wider kinematic chain (lumbar spine/sacro iliac joints/knee etc.) also needs to be evaluated for anything that might delay or upset the healing process.
Once a proper diagnosis of the injury and any associated factors has been established then the treatment (soft tissue work/joint manipulation/ultrasound/laser/exercises etc.) can be applied in the correct amounts and order.
This will require an expert in biomechanics and treatment soft tissue injuries probably with an interest in swimming and its related injuries.
You may well find that to get this to heal properly for high level competition you need a multidisciplinary approach.