Mashaba's performance has come under the microscope in recent times following a string of poor results, the most recent of which saw Bafana suffer their second consecutive defeat in the 2017 Africa Cup of Nations qualifiers.
Much of the criticism has centered around Mashaba's squad selections as well as his regular rotation of the captain's armband.
"I hear people criticising the rotation of the captaincy for instance and the number of players that he has used," Mumble was quoted as saying by Times Live.
"That is the mandate from us. We said he must broaden his pool so that there are more players available on the international stage.
"We are still on the right track and told him not to expect miracles. So we are not going to put pressure on him, at least not for the first two years because he needs to build a team in that period."
Mumble commented specifically on Mashaba's squad selection policy as well as the stumbling blocks the coach has faced in trying to follow his mandate.
"Anywhere in the world, administrators don't go in and tell the coach whom to pick," Mumble added.
"I think that is sacrosanct in world football. We are also very protective, especially when clubs don't want him to select certain players because that is tantamount to telling the coach whom to select.
"There's an established set of criteria that he uses, which is common practice and came out of the technical master plan that we adopted in 2010," Mumble said.
"[But] we are obviously getting to a point where the experiments will have to come to an end because we need to solidify a team going into the AFCON in the next 18 months - a team that is going to play together consistently for some time.
"I think we must all pack our bags if we don't put those building blocks in place and don't do well at the 2022 World Cup."