The arrival of Rooney's former club Everton to Old Trafford on Sunday is a painful reminder of how, despite twice establishing a two-goal cushion against Toffees in the corresponding fixture last term, United were unable to close out the contest.
That failure proved to be crucial in the Premier League title race as it blew the door open to Manchester City, who went on to be crowned champions. It has been a similar story this term, the only difference being that the Red Devils have generally found a way to squeeze out a succession of unconvincing victories. "I can't put my finger on why we are not killing teams off," Rooney said.
"We have scored plenty of goals. It is the most number we have scored at this stage of the season. We have conceded too many and have done throughout the season. But that is the way we have been set up to play. We have to just keep our scoring going."
United do have the edge, though, with further dropped points by their rivals last weekend allowing them to open up a nine-point lead on City, and move 16 clear of Chelsea.
Had it not been for their dramatic collapse last term, when they let slip an eight-point advantage in the space of just four games to hand the initiative to City, many observers would now be writing United up as champions already.
Rooney has no intention of falling into that trap.
"Results are the most important thing now," he said. "Look at Manchester City against QPR - they should have got the win, had a lot of chances but ended up dropping two points.
"That could quite easily have happened to us against Southampton the following night.
"It proves we have to keep picking up the points when we can. Once it comes down to the last four or five games, then we will see what position we are in and work out what we have to do."