There is always something wrong with the fighters during their duels.
Luke is half-trained.
Obi-Wan in the OT is old and slow.
Darth Vader is whereing armor and has all those injuries.
Qui-Gon was getting old and now he has been stabbed through the stomach.
Darth Maul didn't have anything wrong with him until he was sliced in half.
Obi-Wan in the Ep. I is trapped behind a laser wall.
Anakin will kick butt until he becomes Vader.