The star duo have hardly figured together this season.
Macari told the Daily Express: "David Moyes hasn't got those players to turn a game for him and United are suffering. Look at the difference, for instance, Rooney made at Hull. United were 2-0 down after 12 minutes but he supplied the free-kick for Chris Smalling to score the first goal, equalised himself and then played a part in the winner by pressurising the defender to head into his own net.
"If United can get Rooney and Van Persie back together it will turn their season round. I don't care what team it is - Arsenal, Chelsea, Manchester City or Liverpool - if you don't have your two best players, performances will suffer."