Mosimane said they could only blame themselves for not capitalising on a quick start in Atteridgeville, just outside Pretoria, where they were 2-0 up after just six minutes as their Ugandan visitors seemed to suffer from stage fright.
We have ourselves to blame for putting ourselves in this position so we need to take ourselves out of this position
Sundowns had the lion's share of possession in the first leg of their last 32-tie after that, but still allowed KCCA to get back into the game and net a potentially vital away goal in the 69th minute.
"We have ourselves to blame for putting ourselves in this position so we need to take ourselves out of this position. So we have to fight for it. We have the experience, we have the game, we have the personnel.," said Mosimane, voted Africa's Coach of the Year for 2016.
It means a tenuous lead for the return leg of the second round tie in the Ugandan capital where KCCA need win only 1-0 to go through on the away goals rule.
Mosimane says Sundowns will have to defend well in the return but also pointed out his own team's good away record in winning last year's crown. He said KCCA would be forced to leave gaps at the back as they went in search of victory in front of their own supporters
"It won't be an easy game for them either because they have to push everybody upfront to go score And then we can play on the break also because we've got that ability."
KCCA surprised Mosimane with their work ethic and their recovery after conceding goals to centre backs Bangaly Soumahoro and Ricardo Nascimento so early in the game
"They worked hard. They are a hard working team, they really worked off the ball, they fight, they run, they don't give up, they have the hope," he said of the Ugandan champions, who are also current league leaders in their domestic competition.
Sundowns now face the possibility of joining the likes of recent champions who have come unstuck in embarrassingly early fashion in defence of their crown.
Last year it was TP Mazembe who went out before the group phase and two years before that Egypt's Al Ahly were handed a shock second round defeat by their namesakes from Benghazi in Libya.
Mamelodi Sundowns coach Pitso Mosimane says the African Champions League holders are in a difficult position after failing to take advantage of a star-struck Kampala Capital City Authority (KCCA) and not press home their early dominance as they began the defence of their title on Friday night.