In cycling, an average pro level rider can put out around 350 watts for an hour.
So if a pro is doing 350 watts, and I ride right behind him, my front wheel about 3” off his back tire, I can stay there with only putting out around 250 watts.
It follows that he his going as hard as he can, while I am resting a little, as I am not using all my energy.
If I time it right, wait for him to get tired, I will go past him, he will try and catch my slip stream, because I am recovered, I will be able to do around 450 watts for a few minutes, he will lose my slip stream and I will leave him behind. Means I rode him off my back wheel.