The Irish second-row underwent corrective surgery on a bulging disc in his back at the beginning of the month.
He is expected to be out of action until April, ruling him out of the entire Championship, and he reckons he has only an outside chance of making Warren Gatland's tour party.
"It's going to be very difficult," said O'Connell.
"You would imagine the Lions squad is going to be picked on the basis of the Six Nations so it's going to be very difficult to make it on that trip.
"I'd love to get back playing in April and see what happens. I'd love to get going on some tour during the summer, be it with Ireland or the Lions.
"When you look at it, I remember the hype around the Lions four years ago; it seems to be even bigger this year but the big hype is around the Six Nations and the players that show form in the Six Nations.
"It is going to be very tough not playing in that tournament."
O'Connell has a slim chance of making the latter rounds of the tournament but he is resigned to missing out.
"If I was it would be a bonus but I don't think it's going to happen," added O'Connell.
"It will be sometime in April. It would be great if it was early April but I've just got to make sure I get it right and I'm right for the rest of my career.
"You'd never rule it out (the Lions) but I'll be back playing in April so it's probably going to be very tough having not played in the Six Nations."