The 34-22 loss to the Lions at Ellis Park dented the Sharks’ momentum after they had given themselves a platform in recent weeks with bonus-point victories over the Stormers.
Van der Merwe says the performance simply did not reflect the level the team expects of itself.
"As a team, we were all disappointed with the result and the performance we put out. Preparation this week has focused a lot on collective issues to fix. We also know that there were a few unforced errors, and other areas of our game that needed cleaning up, but so far the preparation has been good and we can't wait to rectify our last performance on the weekend."
The Durban outfit currently sits 10th on the United Rugby Championship table, but will take belief from their 21-12 win over the Bulls in Durban when the sides last met in December.
Victory in Pretoria would strengthen their chances of breaking back into the top eight and keeping their playoff and Investec Champions Cup ambitions alive.
Van der Merwe admits Saturday’s encounter carries added importance for their campaign.
While dominance in the collisions is always important in South African derbies, matches played on the Highveld often come down to how well teams manage the kicking game and aerial contests.
Van der Merwe conceded that it is an area where he personally would like to improve following last weekend’s outing.
"The kicking game comes into it with the aerial contest and that's something I work really hard on. Last weekend, I wasn't that sharp in that area and that's something we as a team rely a lot on. So for me personally I want to be a lot better in that space."
Out wide, the Sharks continue to blend experience with youth, with Springbok winger Makazole Mapimpi lining up alongside emerging talent Jaco Williams.
Van der Merwe believes Williams has shown encouraging signs this season and is capable of developing into a consistent performer at this level.
"Jaco is an exciting player. He is still a bit quiet but I enjoy him a lot because he brings a lot of excitement to the team. It's been incredible to see him grow over the last couple of weeks and I think he can still reach incredible heights."
The Sharks team for Saturday’s game will be named on Thursday.