If there is an injury hell, then you might have found the centre-back there, doomed to try to roll some boulder up a hill, only to have his dodgy knees give out each time just before the summit.
But now, after years spent first in the treatment room, O'Brien can at last look forward to regular first-team action. Beginning today against St Johnstone at Fir Park.
"Oh, he'll definitely start," said the Motherwell manager, much to the relief of the football writers with a preview to knock up.
For the first time in a long time, O'Brien steps into the breach. They remain beset by injuries at Fir Park, particularly in defence, with Steven Hammell, Simon Ramsden and Zaine Francis-Angol not yet ready to return and Fraser Kerr suspended.
The sight of his new team-mates struggling only brings back painful memories for O'Brien, a promising youngster beset by so many knocks, niggles and nasty twists that one would not be surprised to learn there was a cackling Nottingham Forest fan somewhere with an O'Brien-shaped voodoo doll and a packet of Poundstretcher hairpins.
He even underwent surgery to repair a valve in his heart, after a routine scan flagged up a problem. This is something, though, on which O'Brien does not want to dwell. "It's in the past; I don't speak about it because it was so long ago," he says.
Of greater concern were a string of footballing ailments. "Two years ago I did my cruciate," he adds, wearily. "I was playing for Derby till the December which had me out till the following season, then when I came back I had a micro-fracture on the same knee so it was never 100%. My career's been stop-start."
He was reluctant to go out on loan last season, he explains, because it was more important to make the sure he was clear, fit and ready to play every week. "Now, I want something to build for every week, a game on the Saturday," he explains. "I'm looking forward to being at a club where I can feel part of it and not just be playing reserves or under-21s every week."
Even this summer, O'Brien rolled his ankle and missed most of pre-season. Next week's international break will be a chance to work on his fitness and for the rest of the squad to recover. McCall can only sigh in relief at the thought.
Over at St Johnstone, meanwhile, two former partners-in-attack have joined forces, six years after they last appeared together. It may sound like an unnecessary sequel to an old buddy-cop movie, but Chris Millar, newly signed on loan from Dundee United, is in fact looking forward to teaming up with his old Morton mate Brian Graham.
"He was a young boy at Morton and I was a little bit older," Millar recalled, casting his mind back.
"He has filled out a bit but he was always tall. He will score goals. This move is great news for us."