In a BBC podcast Horner does say that it is a lot easier for the team when a driver is clearly the leader. "It makes your life a lot easier when there are clear boundaries. Like with Alex Albon, for example. He is still young, but he knows he gets the same opportunities and has the same material as Verstappen. But he also knows that our best chance to win a world title is with Verstappen."
"That's what makes it difficult"
"It is also easier for the driver to deal with that, as long as there is acceptance in advance," continues the British team boss. "It gets tricky when you have two drivers fighting neck-and-neck and both believe they are the best. They use everything they can to get an advantage over their teammate.
"The only person you will be judged against is your teammate because he is the only person on the grid who has the same equipment. So he will either make or break your career. They are called teammates, where that is exactly the opposite of what they are because that person in the other car makes you look like an idiot or someone who does have value," concludes Horner.