Verstappen was holding off his charging title rival Lewis Hamilton in the closing stages of a thrilling race in Austin when he lost time trying to lap Schumacher’s Haas. 

Hamilton closed to within a second but Verstappen was able to benefit from a crucial DRS boost on the main straight heading onto the final lap after finally getting past Schumacher. 

It proved key to Verstappen keeping Hamilton out of striking range as he went on to claim his eighth victory of the season to extend his championship lead to 12 points heading into the final five races of the 2021 season. 

“It’s very difficult to factor into your strategy, the backmarkers,” Horner said. 

“We lost a lot of time behind Yuki [Tsunoda] and then Mick Schumacher was quite costly on the last couple of laps. 

“I thought that was going to cost us the victory because he held Max through the whole last sector. 

“Thankfully he did pick up the DRS on the start-finish straight which at least gave Max a bit of breathing room into Turn 1. 

“But it certainly added to the stress on the pit lane.”

Verstappen was on pole position but lost the lead to a fast-starting Hamilton at Turn 1.

Horner explained that Red Bull opted to gamble on an aggressive strategy by stopping Verstappen early after he reported he could not overtake Hamilton, despite being faster. 

“I think we were quicker on the medium tyre and Max could see that Lewis was sliding around a lot and we were in danger of overheating our own tyres by being stuck,” he said. “So we decided to take the gamble and bang some free air. 

“It was then going to put us under pressure at the end of the race as it was inevitable that Mercedes would run long. We were able to push them to pit early in the first stint by getting Checo in as well. 

“But of course, they then had the ability to go long in the middle stint to give them an eight-lap tyre advantage to the end of the race. 

“Max did a fantastic job managing the degradation and having enough rear tyres left for those crucial final five laps when Lewis was looming large. A phenomenal performance by him.” 

It marked the 18th victory of Verstappen’s career and Red Bull’s first win at the Circuit of the Americas since 2013. 

Asked if it was Verstappen’s best drive yet, Horner replied: “I think it’s up there. He managed the race incredibly well. 

“We didn’t have a great start but we were able to get the win back. It was an aggressive strategy, we went for it and we were able it work. 

“A big win for us at a circuit that obviously Lewis and Mercedes have been so strong at in the hybrid era.”