"I made a terrible mistake," he told Sky Sport Italia. "From then on, it was a totally different game.
"I am the first and only person responsible for this result. I'm more disappointed than anyone, as I was so looking forward to playing."
It's a particularly unfortunate incident, as Conti is the son of Roma director Bruno Conti, who was visibly shaken on the touchline.
Remarkably there are no fractures, but the midfielder has been taken to hospital for tests on potential knee ligament damage.
"I apologised to Daniele on the pitch and then in the locker room afterwards. I went there to get the ball, but then I saw he was down and realised my game was over.
"I did not go in with bad intentions. I told Conti that and what I want to reiterate is that I want more than anything that he can get back on the field as soon as possible.
"I went for the ball and just didn't see him; I was looking only at the ball. I also spoke to his Dad and apologised.
"He told me these things happen, so I reiterated that I absolutely did not go in trying to get the man. I take full responsibility for this result; I put my teammates in a terrible position."