Basso crashed 72km in on the second stage, coming away with only abrasions and a bruised elbow. He got back on his bike and finished 11 minutes down, dashing his hopes for the overall classification.
He has continued to struggle since then, losing 10 minutes on the fourth stage and nearly eight minutes on Thursday's fifth stage.
It is the second consecutive year that the Italian has been hampered by crash injuries. Last year a training crash on Mt. Etna in May put an end to his plans to challenge for the Tour de France title.