Red Bull says it will fill in Max Verstappen before next week's Russian Grand Prix on the steps Honda is taking to improve the reliability of its engine following the Dutchman's two successive DNFs.
Verstappen was sidelined early on by an engine problem at the Italian Grand Prix at Monza and was then hit with another power unit issue at the start of last weekend's Tuscan Grand Prix that ultimately led to the collision that caused his demise from the race.
At Mugello, the Red Bull charger, stranded in the gravel trap on the opening lap of the race, vented his frustration over the radio, saying: "This is what you get with this f**king shit show".
Horner says his driver's disappointment was warranted.
"Max's frustration at another DNF is totally understandable," Horner told the Red Bull website.
"From the very first lap in Mugello he was on it. We had a very fast car and some real progress has been made with the balance of the car.
"That is what was so galling for him. In the heat of the moment when you have gone from the adrenaline of the start to the disappointment of ending up in the gravel trap, it is only natural to vent on the radio.
"We really felt that in the race we could take the fight to Mercedes. He had done the hard work in beating Lewis [Hamilton] off the line and it was going to be game on, but of course that did not materialise.
Horner says his team will regroup ahead of Sochi and inform Verstappen of ongoing developments regarding Honda.
"It was the second race in a row and a huge frustration for him because he is hungry and wants it so badly.
"If he did not have that hunger, he would not be the driver he is, and the one that we all want to watch fight for victories each weekend. He has to get it out of his system now and then look forward.
"We will go through it with him prior to Sochi and discuss what has been done behind the scenes between Honda and the team to help so it is rectified for the next race."
Horner is expecting Mercedes to lead the charge in Sochi, but the Briton is hopeful of throwing a wrench into the German team's works if it can put the Black Arrows outfit under pressure.
"I expect Mercedes to be fired up and pretty dominant as it is their type of track," he said. "But as we have seen this season tyre degradation is an interesting factor.
"They weren't stretched last weekend, but you could hear how nervous they were, instructing their drivers to stay off the kerbs.
"So, it would be great if we can be competitive in Sochi and put them under a little bit of pressure, because that is when things can happen.
"Championship wise, we are very much outsiders now and every race is a cup final for us. We are just going to go for it as we have nothing to lose."