Injury updates 8/22: Connelly, Graham, Lalos, Lattimore and others
Groin injuries are almost always the result of a strain to the adductor muscle.
Things to help avoid injury wouldn't just be stretching but strengthening the adductor muscles through strength training (wide stance squats, sumo stance deadlifts, etc.).
Could be that the S&T staff isn't really focusing on this area as a part of the overall program.