Zlatan Ibrahimovic assumed spot-kick duty on Friday night as the 34-year-old scored his second of the game from the penalty spot after United left-back Luke Shaw was fouled inside Fraser Forster’s area.
When fit, Rooney has been United’s first-choice penalty taker following Robin van Persie’s move to Turkish side Fenerbahce at the start of the 2015/16 Premier League campaign.
Asked if the England and United captain would be upset about being taken off spot-kick duty, former Arsenal striker Thierry Henry played down the significance of the decision.
“He isn’t in that mentality any more. First and foremost he will want to finally win the league again,” Henry told Sky Sports after Friday night’s 2-0 win.
Ibrahimovic scored in the first half with a towering header after the 34-year-old rose above Southampton skipper Jose Fonte and guided a header past Forster.
The Swedish striker emphatically placed his second-half penalty past the Southampton shot stopper to seal three points for the 20-time English champions.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news