Britain's Geraint Thomas was forced to pull out of the Giro d'Italia because of a fractured hip.
The Ineos Grenadiers rider, 34, crashed just before the start of Monday's third stage after a drinks bottle became lodged under his front wheel.
A scan on Monday was inconclusive but a second on Tuesday showed a fracture.
Welshman Thomas completed Monday's stage but lost more than 12 minutes, effectively ending his hopes of winning the race.
"It's so frustrating. I'd put so much work in to this race," said Thomas, who won the Tour de France in 2018.
"I did everything I could and feel like I was in just as good, if not better, shape than when I won the Tour. I was feeling really good. So for it just to end like this is gutting.
"I woke up and wanted to start with the boys and at least help them go for stages over the next few days, but deep down I knew something wasn't right, so we went to get these extra scans.
"It does make the decision easier when there's a fracture in some ways, because obviously I don't want to do any more damage."
Thomas was among the favourites to win this year's Giro before his crash during the neutralised zone at the start of Monday's mountainous stage up to Mount Etna.
He appeared to be riding comfortably despite badly torn kit and landing on his hip.
But Thomas slipped back from the peloton about 25km from the end of the stage.
Ineos Grenadiers doctor Phil Riley said on Tuesday: "Geraint had an MRI and a CT scan this morning which revealed a small undisplaced fracture in the lower part of the pelvis, which wasn't picked up on the X-rays yesterday.
"As a precaution, he will be withdrawn from the race as it's an injury that could easily be aggravated."
What now for Thomas and Ineos?
Thomas' withdrawal is a major blow for Ineos, whose run of five successive Tour victories ended last month after defending champion Egan Bernal abandoned the race when he lost seven minutes to leaders on stage 15.
Ineos must now decide on a new leader for the rest of the Giro, with Tao Geoghegan Hart their highest-placed rider in the general classification at three minutes 19 seconds off the lead.
For Thomas himself, having to pull out of another Grand Tour is bitterly disappointing.
In the build-up to this year's Giro, he had spoken about his burning desire to address his "unfinished business" with the race, having been forced to withdraw in 2017 after another crash beyond his control.
Thomas missed this year's Tour in order to concentrate on the Giro and his preparations had gone well as he finished second at the Tirreno-Adriatico stage race and fourth in the Road World Championships time trial.
Having been denied another chance to win a second Grand Tour, Thomas must now heal from the latest in a long line of injuries and use this pain to fuel his determination to come back stronger next season.
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