The extent of the tyre gradation in Spain caught almost all the teams by surprise, and Horner admitted that it had been "a tough race" for the team.
"The way it panned out it was obvious that tyre degradation was going to be a key factor," he said. "When you are telling drivers not to push because we are saving tyres isn't great for the sport of for the fans.
"We need to push the drivers harder and allow them to drive properly," he insisted. "It is the same for everyone but we all know they are marginal. It's tough we were too tough on them early on."