It is hard to say one thing he can do instead without knowing his whole program. Dead lifts are just one lift in a program. There are no magical lifts. Just good progressive programs that pay off with effort. Every athlete has different needs and their programs should be adjusted accordingly. Hopefully, his strength coach can make adjustments to his program if he is experiencing pain and his form is good. Pain is your body telling you something is wrong. It is either an injury or bad form. It is also possible his mobility is not good enough to do the lift properly. The other exercises that were given are all good alternatives, especially the single leg versions as these are usually more back friendly since the weight must be lowered. But even these can cause problems if done with poor form or an injury.
@Andrew-- A trap bar dead lift is just a dead lift done with a trap bar. It provides relief for those that do not have the mobility necessary to do the dead lift with good form. A trap bar has handles so that the athlete does not have to get as low to get the bar. Another way of doing dead lifts for those without the mobility is to elevate the bar on blocks. One could also do rack pulls by placing the pins in a squat rack on the lowest rung and putting the bar on that.
Nothing that causes pain should be done. Hopefully his strength coach can help with this problem and if not maybe a qualified professional in your area can help. Back pain is not something to take lightly.