The Red Devils striker stressed the importance of performing professionally after they overcame Reading in a 1-0 win, though he did admit they were well-placed to win the league.
The win puts Rooney's team 15 points clear of Manchester City at the top of the table following their close rival's surprise 2-0 defeat against Everton earlier that day.
With nine games remaining, the England international admitted that they are well-positioned but insisted that they must focus on doing a professional job.
"We knew the three points was the most important thing today, especially with City dropping three points," he told ESPN. "It was a tough game, but we held on and that was the most important thing.
"We knew that the most important thing was our result. We had to make sure we were right and we got the three points regardless of what happened. It was great that City lost but we had to make that up with the three points.
"We are professionals. We know we're in a great position with nine games to go, 15 points clear. But we're professional footballers, we have to go out week-in week-out and do our jobs. Whether we're top, or second in the league you just have to keep going and try to win the games."
Rooney was also quick to give credit to managerless Reading as, despite his early opener, the Royals continued to battle and kept the game close until the end.
"We expected that [from Reading]," he added. "They're a good team, but fighting to stay in the Premier League, so those matches are always tough. Full credit to them, they gave us a good game."