Geraint Thomas crashed out of Tirreno-Adriatico on Sunday during the early part of the time trial stage.
According to his Barloworld team, Thomas crashed on a right hand corner early in the time trial and went over the guardrail. His bike ended up in a tree and he went down a banking. He landed heavily on his face cutting his lip and eyebrow.
In hospital he was diagnosed with a broken nose and a micro fracture of the ischiopubic bone in the groin.
According to the Team Barloworld doctor, Thomas will be out of action for at least 20 days and so will miss Milan-San Remo and the Tour of Flanders.
Thomas had targeted the 30km time trial at Tirreno-Adriatico and was second fastest at the first time split when he crashed.