"I got into a bit of a dark place. I couldn't even do any exercise and I had conversations with my partner about retirement. It was really hard. I love playing footy, it's my job and I couldn't do it."
Coles, 30, was sidelined for four months this year and what will make his latest injury at Stade de France so frustrating is the fact that he was starting to return to the Coles of old - the best hooker in the world. As with many ACL injuries, it occurred away from contact from a twisting motion.
Coles' try which opened the scoring for the All Blacks was a perfect example of his pace and awareness. Timing his run on to Beauden Barrett's pass near the France try-line, Coles ran the perfect out-to-in line and gave the two defenders no chance.
It was his 56th test. His 50th happened to be the Bledisloe Cup test against Australia in Dunedin in August, a classic come-from-behind victory for the All Blacks and his first since his concussion problems.
Facing the media in the days beforehand, Coles was asked about his fears of another head injury.
"There is always a bit of fear, that is just natural," Coles said. "It is just not letting that fear control you. When I am out there, training and doing contact, I am not thinking about my head. I am just making a tackle and throwing into the lineout.
"That is what I have learned, don't let it control you. Once I am in the moment ... I am just playing footy."
It may seem of little comfort, but his knee injury rehabilitation should be far more straightforward than his return from concussion. Surgery will be followed by rest and then exercise and physiotherapy and improvements should be felt by the week, whereas a return from concussion is far less predictable.
Coles, missed several matches for the Hurricanes last year with a rib injury so has had more than his share of physical problems. He has apparently accepted his latest one with a philosophical attitude, but it will still be hard to stomach.
In his absence next year, exciting prospect Asafo Aumua, on the reserves bench for the All Blacks for their match against a French XV in Lyon on Wednesday morning NZT, will battle with Ricky Riccitelli for the No2 jersey.
Codie Taylor is now the incumbent hooker for the All Blacks, with Nathan Harris the back-up.