The reverse thrust on the MD88 can block out the rudder so rudder control could have been lost when max reverse was applied shortly after touchdown causing the deviation to left as the report indicates. Reducing or removing reverse thrust would once again make rudders effective. This would have been required as soon as the drift to the left began to return to center line of runway. Reverting to manual braking would also help return to centerline with differential braking. RWY 13 of course doesn't give you the luxury of cancelling reverse for long.