Wednesday's 1-0 win over a Rangers team hoping for a repeat of their surprise goalless draw at Old Trafford and playing with a similarly defensive approach, will be quickly forgotten.
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Rooney, however, will be relieved that his first start since September following an ankle problem went off without mishap and was capped by a crucial spot-kick after 87 minutes in Group C.
Certainly Sir Alex Ferguson was happy to focus on a positive from his key player who has endured a torrid few months by any standards including media stories of marital infidelity followed by a bizarre episode in which he threatened to quit the club only to pocket a new five-year deal instead.
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The United manager, a former Rangers centre forward himself, said: "He's never been short of courage and it was a fantastic penalty, a very good penalty.
"He needs games and the way we're going to do it is by keeping him on the pitch for 90 minutes and that will continue now as we try to get him to his level.
"He's rusty, he's needing games, that's obvious but it's a start for him."
Rooney, who had earlier hit the woodwork, may need time on the pitch but his appetite and workrate are certainly not in question, witnessed by his scampering to pick up the ball to take the penalty after Steven Naismith caught Fabio in the face with the clock running down.
The England striker beat Allan McGregor with some aplomb - he found the left, low corner as the keeper dived the other way - to score only his second of the season.
The goal was a fair reward for United who had huffed and puffed to break down the Rangers defence without any luck.
Ferguson for once erred on understating the matter later when he commented: "With the amount of possession we had, I think we deserved the win."
With Valencia beating Bursaspor 6-1, the Scottish champions needed a win to keep their already slim hopes of the knockout phase alive but seemed intent solely on avoiding embarrassment despite home advantage.
Only Kenny Miller threatened to upset United dominance with a header which dropped narrowly wide of Edwin van der Sar's post.
Rooney saw a header of his own hit the bar at the end of the first half and Michael Carrick also wasted a good opportunity.
Rangers have the consolation now of Europa League qualification but manager Walter Smith thinks they will struggle without new signings in the New Year.
He said: "If we don't get any help in the January transfer window we could have a struggle again because we're right down to the bare bones."
