The Scot has confirmed he plans to retire at the end of the 2014 season in a video interview with Dutch cycling magazine Wieler Revue. "It has been quite organic really," he said. "You always think it is going to be a definitive moment, but it hasn't been. It has kind of crept up and I am suddenly realising it is time.
"I think my body is actually getting stronger. It is just I don't want it or need it as much as I once did. It is very much a conscious decision. I can still be on top of the game - I know that - but it is a lot harder for me now and I want to be on top of my game next year, so I know I can get that out of me. With the motivation of knowing it is my last year, I know I can get the best out of myself."
Millar, 36, a winner of four Tour de France stages and a Commonwealth Games gold medal during his 16-year career, is a self-styled fervent anti-doping campaigner.
Suspended from professional cycling between 2004 and 2006 after admitting to taking the banned blood boosting hormone erythropoietin (EPO), he now sits on the athletes' commission of the World Anti-Doping Agency.
Millar, who rides for Garmin-Sharp, has long hinted that 2014 would provide the perfect swan song to his time on the bike. Two years ago he told Herald Sport he had "a romantic idea that I will retire at the Commonwealth Games in Glasgow", adding he quite fancied "a block party - go out in style."
Having taken Commonwealth gold in the time trial and bronze in the road race in Delhi three years ago - an experience which Millar has dubbed his "redemption" - he has made no bones about his desire to repeat that success in Glasgow.
He described competing in the British National Road Race Championships in June as one of the most spine-tingling moments of his career, paying tribute to the support of the partisan Scottish crowd.
"It was phenomenal: I now know how Thomas Voeckler feels in France," he said. "I've never had that in my whole career in a race, the amount of people shouting for me. I liked being called 'Davie' as well. It's amazing how much that lifts you and makes you want to not let people down. I'll be back next summer - I can't wait."
Family life is another key consideration. Millar lives in Catalunya with his wife Nicole and their two sons - Archibald, two, and five-month-old Harvey. "I want to be at home more," he told Herald Sport earlier this summer. "That is something which will provoke me into action in the next couple of years."
Exactly what the future will hold after retirement is less clear, but Millar has previously ruled out a behind the scenes role with a team. "It has never interested me, going into coaching or being a directeur sportif," he said. "That's not my forte."