The crash happened in the final time trial. The Dutch rider was fighting to try to take the overall victory, but the vicious cross winds was difficult to handle and suddenly he was down.
"I'm not a doctor but it looks like a broken collar bone or shoulder. It's too early to make a call but at the moment it looks like we'll have to bring in Guillaume Van Keirsbulck," team boss Patrick Lefevere told Cyclingnews.
Terpstra has been in quite good shape lately, and he was one of the riders to fight the hardest at last week's E3 Prijs Vlaanderen. He would surely have worked the hardest possible to make Fabian Cancellara (Leopard Trek) and Philippe Gilbert (Omega Pharma Lotto) lose at Sunday's Tour of Flanders.
"With him and maybe and Sylvain Chavanel we could have played a couple of jokers in Flanders," Lefevere said.
"We'll problaby go with eight riders but we've got riders who can't come in because they're either injured or have other goals. We lost a strong rider today who would have made it into the final on Sunday."
Tom Boonen, a two-time winner in the race, will participate and perhaps he can win, even though it doesn't seem likely.