Replacement striker Sanni Issa scored the lone goal for the men in black late into the match while the capital city side pipped a tough Nadroga side with the same score to book their spots in the semis.
The Babasiga Lions played with only 10 players as Vikrant Chandra was given the marching orders for tackling Abbu Zahid late into the game.
Both Ba and Suva have 6 points.
Labasa and the Stallions are out of the tournament following their losses and their match next Friday at Prince Charles Park in Nadi will be a formality.
Lautoka is leading pool B with 6 points, Nadi and Rewa have 3 points each while Navua is yet to win.