The Australian, 26, began the race working for team leader Tejay van Garderen but with the hope of riding high in the general classification. Earlier this year he placed second overall in Tirreno-Adriatico.
"I'll continue as normal on stage four, but obviously I'm five or six minutes down and that's a big margin after three days," Dennis said.
"Anything can happen. I'm not going to thrown in the towel and say 'stuff it' but I have to be realistic and say GC is done. I'll keep doing what I was planning, riding as if it isn't done and still getting that experience and still look after myself for three weeks."
The crash happened soon after the race split with 10 kilometres to race. That split saw Quick-Step ride free with eventual stage winner and new race leader Fernando Gaviria.
"We were making an echelon to bring that group back and a team Bardiani guy came around me as I was trying to start it. He just turned left on my front wheel and took me out," Dennis added.
"I didn't even have a chance. There was no split second where I could try to hold it up. I was down on my right before I knew it."
"He got back up, he got a new bike because his other was broken, but by that point there were four or five groups ahead," sports director Max Sciandri explained.
"It was a big blow. We are only in the third day, but it is a blow for his morale."
Dennis fell on his right side and "has a fair bit of road rash and superficial contusions," reported the team doctor. "He is lucky to escape with nothing serious and will be able to continue racing."
"The shower hurt, but it's mainly my neck," Dennis continued. "I have a headache from the jarring of going down, I have to see the physiotherapist and get that fixed."
BMC lacks a second classification card to play in the mountains now and must rely on van Garderen. Van Garderen is racing his first Giro d'Italia after having focused on the Tour de France in years past, including placing fifth twice.
"For the Giro, it's going to be wait and see. That time loss is a lot, but if he has the legs he can go in the escapes," Sciandri said.
"Last year, Darwin Atapuma managed it well and finished ninth after losing three minutes in the time trail. You can still do many things if you have the legs. The Giro is long and there are many kilometres yet to race. So he can try different things."
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