England captain Dylan Hartley has been ruled out of the tour because of concussion and Sarries star Farrell is among the favourites to replace him.
"It is up to England whether he (Farrell) goes but I am certain he will go," McCall told reporters.
"He will be a brilliant captain. He is ready to do that job and has the respect of everybody. He has a fantastic rugby mind but he is also brilliant at getting the best out of his team-mates. Both these things combined make him an ideal captain."
Farrell, who has 58 caps for England, did captain Eddie Jones' side during their Six Nations defeat by France in March.
Jones is expected to name his squad for the South Africa tour next month with the three-Test series opening on June 9 in Johannesburg, before England meet the Springboks again in Bloemfontein and Cape Town later in the month.