Team Sky's Peter Kennaugh suffered a heavy fall in the Tour of California on Tuesday which could put his Tour de France place in question.
The Manxman suffered "a suspected broken collarbone", according to his team's website, after hitting the deck late in stage three of the American race.
The injury has yet to be confirmed but if it is as bad as feared, Kennaugh risks missing July 2's Grand Depart from Mont-Saint-Michel.
In addition to the damage to Kennaugh's Tour prospects, Team Sky sport director Gabriel Rasch described the crash as coming at "the worst possible time" for the team.
Rasch said: "We were looking all good until Pete crashed. When he crashed the guys waited for him and pretty quickly we saw he couldn't carry on.
"We still have some good chances this week, with Danny [van Poppel] in the sprints and we will see how Lars Petter [Nordhaug] is. There are a couple of stages with some pretty hard finals so we will see how he goes there."
Julian Alaphilippe won the stage and claimed the overall race lead for Etixx-Quick-Step.