It would be necessary to know before each race, or at least when the contract is signed, what the requirements are for a particular sponsor. For example, if we generally know that sponsor A is aiming for 1-3 places on average, while sponsor B is aiming for a 5th place, in a hectic league (with players of different strengths), the manager might choose the sponsor with lower requirements, especially if he is looking for or training a driver and not the results of the race.
I've run into a situation where for a few races my sponsor was satisfied with 1-3 finishes, and then in a weak field my rider and team were expected to finish 1st, which was impossible given the strength of the competition.