Simon Gerrans is a late withdrawal from the Milan-San Remo classic because of illness.
It robs BMC teammate Greg Van Avermaet of an important ally for the first major one-day classic of the season.
Gerrans won the race six years ago, one of the biggest highlights in his outstanding career.
But after switching to BMC this season, the 37-year-old was to ride on Saturday in a support role for his star Belgian teammate.
"Gerrans developed a respiratory infection at Paris-Nice which triggered his asthma," said BMC doctor Max Testa.
"We hoped he would be able to recover in time for Milan-San Remo but over the past two days, his condition has worsened.
"Given the poor weather and the length of the race, it is in Simon's best interests to not line up on Saturday.
"Fortunately, Simon will be able to resume training in a few days and his illness won't affect his race program."
BMC have drafted in Francisco Ventoso to take Gerrans's place.
Van Avermaet won the Rio Olympics road race and also took out last year's Paris-Roubaix.
Michael Matthews (Sunweb) and Caleb Ewan (Mitchelton-Scott) are the best Australian hopes in Saturday's race.
Milan-San Remo and Paris-Roubaix are among the five sport's leading one-day classics.
