Well, Derrick wasn't technically lying post-game Sunday when he said his groin wasn't bothering him. There was no word form the team either way on Rose's (or anyone's) condition on Monday, but KC Johnson has an unfortunate scoop:
Rose, for starters, tweaked an ankle at some point in Sunday's game, which he finished. The extent of the injury is unknown, however sources said Rose wore a walking boot on Monday and his availability for Tuesday's shot at redemption against the Knicks is a game-time decision.
I don't think anyone noticed anything during that game. In fact, Rose made some of his more athletic moves to start the overtime period. Though perhaps he was just running on adrenaline at that point.