Amakhosi secured their second successive PSL win when they edged out the Team of Choice 1-0 thanks to Dumisani Zuma's second-half goal.
Left-sided player Zulu was replaced by defensive midfielder Willard Katsande just 26 minutes into the match which was played at the FNB Stadium in Johannesburg,
"It was very clear. I was hoping we were coming into a winning mentality in particularly this area (left flank). I was not expecting the long balls coming into this area all the time," Middendorp told SuperSport TV.
"Then you see the value of (Willard) Katsande. You see Katsande was necessary to change and not wait till half-time. It has nothing to do with the quality of Philani Zulu," he explained.
"He is another type of midfielder, and but at this moment it was very clear we needed Katsande, a winning-ball midfielder and I think he has done well," he added.
The German tactician also pulled out forward Billiat prior to the start of the second half and he replaced the 2015/16 PSL Player of the Season with teenager Nkosingiphile Ngcobo, who was making his official debut.
"We needed a different approach. We had some moments where I'm missing someone to drive into the front," the former Maritzburg coach said.
"He (Billiat) was injured. We have to give him a little bit of time. I know he's a fantastic player, but it didn't work to our advantage," he said.
"I decided to bring in another type of player in the centre with Bernard Parker co-operating with a little more power and more heavyweight, and with Ngcobo and Zuma light-footed from the side. The inverted position from Zuma brought us a goal," he concluded.