What Causes Back Pain When Diagnosed With Herniated Disc?

My son is in the volleyball club at his school. Japanese school teams are very serious and he practices 6 days a week with lots of jumping and spiking as well as regular games. He had some back pain, but mostly in his bum and legs with some numbness. It hurts more when he is still than when he is moving. He had an MRI and they found a herniated disc in his lower back. The doctor advised 1 month no volleyball. He did say that there are athletes who still keep playing and he didn t seem insistent that he had to take the time off. At the same time doctors in Japan often seem very noncommittal to me. My son insists this is the height of tournament time and the worst time to take off. He promises to take a month off after 6 weeks when the peak season ends. But this also means he will be jumping up and coming down spiking etc strenuously for the next six weeks, because as I said, schools take their sports teams very seriously. Should I let him have his six weeks or should I insist he takes a month off now and see?