launched Manchester United's bid for a fourth successive league title with a first-half winner against promoted Birmingham City at Old Trafford.
United, who had begun their last two Premier League campaigns with Old Trafford draws against Reading and Newcastle, rarely looked like dropping points against Alex McLeish's team following Rooney's 34th minute opener.
But the victory did not come without a cost for United, who saw defender Jonny Evans limp off in the closing stages with a recurrence of an ankle injury that leaves the Northern Irishman doubtful for Wednesday's trip to Burnley.
With Rio Ferdinand missing this game with a thigh strain, and Nemanja Vidic, Gary Neville and Rafael da Silva already sidelined due to injury, the defensive worries are beginning to mount for manager Sir Alex Ferguson.
Rooney's goal ensured a winning start for Ferguson, however, in a game that should have resulted in a much more comfortable victory for the champions.
Prior to Rooney's goal, a predatory tap-in after he had headed Nani's cross against the post, the England forward had forced Birmingham goalkeeper Joe Hart into a stunning fingertip save from a 30-yard shot.
Birmingham almost equalised three minutes later when Patrice Evra headed Franck Queudrue's header off the line, but Hart was called back into action early in the second-half when he saved well from another long-range Rooney effort.
Even though United could no longer count on the penetration of Cristiano Ronaldo, Birmingham's defensive tactics saw them at times play with ten men behind the ball.
The tactic encouraged United to camp in the Birmingham half and Dimitar Berbatov went close to doubling the home side's lead with a header that was cleared off the line by Lee Carsley on 71 minutes.
Birmingham introduced £9.2m club record signing Christian Benitez in a bid to salvage something from the game and the Ecuadorean forced a stunning save from Ben Foster on 78 minutes after escaping from United substitute Wes Brown.
United avoided any further scares, however, as they claimed their first three points of the campaign.
But it could have been 2-0 had Hart not saved well from Michael Owen in stoppage time after the former Liverpool forward had beaten the offside trap.