Sunderland host United on Wearside later today.
O'Shea told the Mail on Sunday: "It was weird going down to Old Trafford last season and seeing him as the manager. It was incredible, you know, but I’m sure it’s given him a taste of what’s to come.
"When we won there it wasn’t nice for Giggsy in that sense when he was the manager, but for us it was so crucial for Premier League survival last season. That was a special day."
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