Wednesday marks exactly 20 years to the day that Giggs made his United debut against Everton, though he was unable to celebrate the anniversary by securing victory over Chelsea on Tuesday night.
While a few one-club men still exist in English football - Steven Gerrard, Jamie Carragher, Ledley King and Tony Hibbert among others - Giggs' achievement in reaching the milestone of two decades in the top flight is unparalleled in the modern era.
And even though many of Giggs' team-mates have been around Old Trafford for some considerable time themselves - O'Shea, Paul Scholes and Wes Brown included - they are lost in admiration for the 37-year-old.
With Giggs having signed a one-year contract extension earlier this year, O'Shea feels he could carry on for at least another three years.
"Without a doubt,'' O'Shea said. "His physical shape hasn't changed since I've known him and he looks after himself so well.
"Depending on injuries he could easily carry on, although I am sure he just wants to take it one season at a time. He is just enjoying it so much at the minute so I can't see why he can't but I'll let him decide on that.''
If nothing else, Tuesday's game allowed Giggs to equal Sir Bobby Charlton's record of 606 league appearances, another record in addition to the scores the Welshman already has.
Indeed, in the modern era, the only player O'Shea can think of that is remotely comparable is recently-retired Italian legend Paolo Maldini.
"You see how the manager has built squads and Giggsy has been a vital part of every single one of them,'' he said. "It's just incredible. Maldini springs to mind with AC Milan but I think Giggsy has even gone past him."
Giggs' new one-year contract means that he could certainly run Maldini close, but the United winger remains 41 league games shy of Maldini's total of 647 games for AC Milan and also 39 short of his overall total of 902 matches.
Nonetheless, O'Shea believes Giggs can be considered nothing less than an "absolute legend" at Old Trafford.
"The speed and the balance he still shows to go past whether it be an old, experienced defender or a new, up-and-coming young strong defender is incredible," O'Shea said.
"Every cliche in the book has been used about the man already and I am sure they will be said many times again. He is an absolute legend.''