That scenario seemed highly unlikely after the Londoners lost both their opening tournament fixtures at home to the Scarlets and away to Clermont but they hit back in fine style with successive wins over previous pool leaders Racing Metro last month.
And now, with a number of big-name players returning from injury and a host of youngsters at home at the top level, O'Shea has plenty of reasons to be positive at the start of the year.
"It has been a real test for us, especially for the young players we have thrown in to cover for all the injuries, but those youngsters are now ready for anything and can step into the side at any time knowing what is required of them, and we know exactly what they can do," said O'Shea.
"You have to give credit to the character of the side for some of the results they have pulled out of the bag during the period when we had all those injuries - like winning at Welford Road (against Leicester) and Newcastle, beating Gloucester, and those two wins over Racing Metro.
"Coping with that is what it takes to be successful. It's been a case of accelerated development for some of them and we will not only see the benefits of it this season but also in years to come.
"With all the players we have coming back to fitness, we can only get stronger, and we feel like we are now getting back to the level we were at before. We have some big games coming up, with Northampton followed by Clermont and Scarlets in the Heineken Cup, but every game is a big game for us now."
Quins head to high-flying Northampton in good form having lost just once in eight Aviva Premiership and Heineken Cup fixtures since their 23-16 defeat at Clermont on October 20.
Their only reverse in those competitions came in the league at Bath four days before Christmas and they were convincing 22-6 winners over Exeter last time out.
More success this weekend would be a huge boost for the clash with Clermont at the Twickenham Stoop, a fixture in which Quins know that picking up four more match points than Vern Cotter's side would ensure their hopes of a Heineken Cup quarter-final would be in their own hands heading to Wales on Sunday, January 19.