Onyango said the fans should put behind them the disappointment of last weekend's barren draw against Anse Re Union in a Confederations Cup match and rally behind the team.
"We understand the fact that our fans are still disappointed that we did not win last weekend but this is something they need to get over and stand by us when we play Tusker," he told Goal.com.
Onyango said they respect Tusker a great deal considering that the brewers are the defending champions of both the local league and the DSTV Cup. He insisted that the team still has some way to go and will pick up as the season progresses.
"As the head coach has said, the season is just starting and we need time before we pick up. I am asking our fans to be patient."
His Tusker counterpart Samuel Odhiambo said the team will not be intimidated by the huge fan base of their opponents.
"We have learnt to play against them even with their many fans. We always encourage ourselves to focus on the job at hand and so far it has worked for us. Saturday will be no different."
Tusker coach Robert Matano said they are determined to retain the trophy they won last year with his Gor Mahia counterpart Zradvko Logarusic pointing out that the team still needs time to pick up their winning ways.