'Rama' has taken over the armband from Alje Schut, who returned to Holland recently after skippering Sundowns to League and Nedbank Cup honours in a three-year spell at Chloorkop.
Mphahlele started his reign in Downs' 4-2 loss on penalties to Bloemfontein Celtic in the MTN8 quarter-finals last night.
"He has qualities," Mosimane says of the defender.
"He has captained the junior teams. He has pedigree and leadership qualities and we are happy with the appointment of Rama.
"He is not Schut, he is Rama. He is the right choice for us. The players have welcomed him and let's see if can lead."
Mosimane also revealed goalkeeper Denis Onyango and Thabo Nthethe form part of the team's leadership core.
"Our second captain is Denis Onyango and the third one is Thabo Nthethe. Thabo was captain at Celtic, Onyango has been captain for Uganda until now, so the leadership is there."