The Sun says the Portuguese star wound up Arsenal by playing keepy-uppy towards the end of his starring show in the 4-0 FA Cup fifth-round thrashing.
Moments later, a clearly frustrated William Gallas took a kick at Nani and could now face an FA charge.
The FA will wait for the report from referee Alan Wiley before deciding whether to take action against Gallas.
But the Frenchman seems certain to face a charge and United boss Sir Alex Ferguson reckons it would be fully justified.
He said: "I thought Gallas should have been sent off. The referee must have a look at that again."