Horwill captained the Queensland-based franchise to the southern hemisphere's premier club crown in 2011 but the Reds were on the wrong end of a 61-8 scoreline against the Bulls on Saturday night.
The Reds conceded eight tries in a humiliating result at Loftus Versfeld, with critics immediately writing off their chances of retaining their title.
But the giant second row insists his men will prove that the comprehensive reverse was a one-off by getting back on track against fellow Australians the Force in Perth this Saturday.
"It was a very uncharacteristic performance from us," was Horwill's assessment of the horror show in Pretoria.
"We need to make up for that, and it starts this weekend.
"That's the beauty of this competition - it continues to roll on. We need to stand up.
"When our backs are against the wall and people don't give us hope, we've performed. It's something that's been a trademark of our team over the last couple of years. One bad game doesn't make you a bad team.
"We need to make sure we learn from this and make sure we put in the performance that will get us back on the right track."
Those sentiments were echoed by Reds coach Ewen McKenzie who remains convinced that the manner of defeat to the Bulls will be a one-off.
McKenzie admits that he was far from happy with the display on the High Veld but he was quick to highlight the manner in which his team continued to want to attack, even if it cost them four tries in the final 15 minutes.
"Even the last scrum of the game was probably indicative, we were still attacking from our own goal line,"said McKenzie.
"Maybe that's silly, I don't know. But in the end that's the way the team functions, we try and play and it didn't work.
"A week is a long time in this sport … it doesn't mean we have to give up. We won't be giving up.
"We'll take stock and dust ourselves off and keep going.
"We're not going to die in a ditch. It's not our finest hour, but it's not the end of the competition either."