The Republic of Ireland defender spent almost 12 years at previous club Manchester United as Sir Alex Ferguson's men took English football by storm and made a major impact in Europe.
He arrived at the Stadium of Light during the summer of 2011 with an enviable collection of honours, including five Premier League titles, plus FA Cup, League Cup and Champions League winners' medals.
However, given the predicament in which the Black Cats found themselves just a few weeks ago, O'Shea insists top-flight survival this season would represent a genuine achievement for his current employers.
Asked how he has coped with fighting at the foot, rather than the top, of the table, the 31-year-old said: "Look, it's one of those things, that's just how things have turned out.
"But success for certain teams can be measured in different ways all the time.
"If we, Sunderland, survive in the league, it's obviously going to be a success because we were in a precarious position.
"We are still in a small bit of a precarious position, but thankfully we have the power in our own hands to survive that, and we have to continue that."
The upturn in the club's fortunes - they sit five points clear of the drop zone after successive victories over derby rivals Newcastle and high-flying Everton - has coincided with the arrival of Paolo Di Canio on Wearside as Martin O'Neill's replacement.
Chairman Ellis Short's decision to dispense with the services of the Northern Irishman was not greeted with universal acclaim, and the identity of his successor, given his back story, also failed to meet approval with some sections of the Black Cats support.
However, what is not in any doubt is the impact the 44-year-old Italian has made in his first few weeks in the post, with his players having thrown off the shackles of dwindling confidence to respond to his methods in fine style.
O'Shea said: "It's one of those things, the more games you are winning, the more you enjoy football, so definitely the last few weeks have been a bit more enjoyable.
"It's the same in any sport, whether it be golf or rugby. When you see players with confidence, you can take it to a whole new level.
"The class of the player will always come out on top if they are doing everything properly training-wise, and we have got to stick to that."
Sunderland's revival will be put to the test on Monday evening when they head for Aston Villa, whose need for points is even more pressing.
Paul Lambert's side currently occupy the last safe spot in the table, just two points ahead of Wigan, who have a game in hand, and three shy of Newcastle and the Black Cats ahead of them.
Victory for Villa would pile the pressure on the Latics and drag Di Canio's men back into the relegation mix, but defeat would severely dent their hopes of escaping the drop.
But such is the positivity within the Sunderland camp that they will travel to the midlands targeting another three points.
O'Shea said: "The way we approach games now, we are looking at being a lot more solid, the unit that we have, but also we have been looking at ways to hurt teams, getting more players into the box.
"That's something the manager has been working on in the last few weeks, and if we continue to do that, the players that we have will cause teams problems.
"They are big pressure games we have left, but ones we have been able to cope with and ones we have been enjoying also."