The Soweto giants were dumped out of the Nedbank Cup after losing 5-4 on penalties following a 1-1 draw after 120 minutes on Saturday afternoon.
"Ja, so a penalty shoot-out in the end not qualify us is a little bit of a situation where probably the team lacked a little bit more luck in the end, [a team] a bit more tougher made it," Middendorp told SuperSport TV.
"It was very difficult regarding the field, this passing, a lot of possession moments where we missed the ball too long or the ball not getting into the direction of our players.
"It's really not to stand here and look for excuses but I think everyone who was part of this afternoon knows it was a little bit of up and down and good, unfortunately we have not made it, we have to compliment the opponent, congratulations to Highlands Park."
The German tactician explained the reasons behind his substitutions just after the break, which saw Anthony Akumu and Bernard Parker withdrawn for George Maluleka and Dumisani Zuma.
"I think actually [Anthony] Akumu had his first 45 minutes, we had a bit of a miscommunication, not really as we wanted to see it. George [Maluleka] is good at complimenting [Khama] Billiat in the central, we got a little bit of the ball in this passing.
"What we tried to do, receive it and passing it through the midfield, good. Dumisani Zuma is always a player who can win one against one, with his variability can give us something.
"In the end we have seen it but, through the length of the entire extra-time, you need a field. You need something, if you want to do your dribbling, if you want to do your combination passing, it [more space] was not there, good that's the reason why I changed," he added.