The Red Devils beat Aston Villa 3-0 on Monday night to clinch their 20th league title but Rush feels there may have been an element of luck.
He also joked that at least Liverpool are still ahead of United in terms of European cups despite their old enemies going two clear in the domestic trophies.
"They were lucky! No, they were by far the best side," Rush told media in Melbourne.
"They've gone two ahead of us in the league now but we've still got five European cups."