Alwanga has managed just three goals in 13 matches this season, a poor return compared to the 11 goals he scored in the last campaign.
The former KCB striker was on target when the Slum Boys emerged 2-1 winners against the Bankers in their previous meeting.
“The first leg did not work out well for me but I have started the second leg very well. I am hoping for better fortunes because we have to score many goals to remain in the title race," Alwanga told the club's official website
“I was at KCB for a very long time and most of their players know me very well. It will be a tough match but I hope to score or provide an assist."
Mathare United will play KCB on April 3 before facing Tusker three days later.