The Bulls have emerged from a rough patch of form, which included losing seven games in a row in all competitions, with two impressive come-from-behind wins in the last couple of weeks.
The beat Pau 26-24 in the Champions Cup two weeks ago, thanks to a late Nizaam Carr try, before pulling off a similar feat against Edinburgh in the URC last weekend after preventing them from scoring a single point in the second half.
According to Coetzee, the two results have given them confidence that they can give the Lions a bit of payback at Ellis Park this coming weekend.
"The two wins were really awesome for the group's morale," he said.
"The confidence is very high and the guys are just happy. We had to get back into that winning habit.
"Our defence really took a massive step up on tour. We managed to rectify the mistakes from the previous games, those soft moments that really cost us.
"We've got a tough derby waiting for us now at Ellis Park, so it doesn't get any easier.
"The main focus now for the group is just to recover from the tour and then we'll put all our energy into a quality Lions side this weekend.
"It's about which team pitches up on the day and uses the opportunity. But they had our number the previous game and it's something we're looking to rectify.
"They're a tight group and you can see how mature they are in the way they approach things and situations on the pitch.
"It's going to have to be a full 80-minute performance [for the Bulls to beat them]. Starters and bench, it has to be buy-in from everyone.
Especially against a side like the Lions, because they will punish you. For our campaign's sake, it's a must win," he added.