The initial medical assessment is that Warbasse (Aqua Blue Sport) will be out of action for six to eight weeks, and that he will need surgery.
Warbasse was one of several riders who fell when they collided with an obstruction in the road, a mountain bike, breaking a bone in the thumb of his right hand. Merhawi Kudus (Dimension Data) was caught up in the same crash and also abandoned.
"I knew that [my thumb] was gone as I tried to ride on my bike, but it felt like my hand split in two when I put it on the handlebars," Warbasse said in a team press release.
"Then I got here to the hospital, and I have been sitting waiting to [get] my cast on my right hand. My left wrist started to swell up, so I have had to go back and get an X-ray. I am waiting to hear what the deal is with that.
"My memory of the crash was that there was a mountain bike laying in the middle of the road. We were in a crosswind section in the gutter. We were full gas – I didn't see the mountain bike until it was too late, until it was in front of me. Either I hit it or someone else hit it – I am not sure.
"I went flying – it was cheese grater pavement, so I have lost a lot of skin. I just want to say a huge thank you to the people who have sent me their best wishes. It is such a shame to leave the Vuelta, but hopefully I will heal fast. Best of luck to the rest of the Aqua Blue Sport boys for the rest of the race."
Warbasse won a stage of the Tour de Suisse earlier this season, prior to taking the American road title. He completed the Vuelta a España for a third straight time last year with IAM Cycling, finishing 49th overall.