Leading by only 150 points and defending 250 from his title win in Marseille last season, Medvedev will drop back to world No 1 on the week commencing March 14 when those points come off.
Having made the semis in Acapulco, the 13-time title winner earned 180 ranking points but could have racked up 300 for a finals showing and 500 for winning the title.
Had he defeated Nadal, he would have led Djokovic in the rankings by 270 points and still been world No 1 when his Marseille points came off, and could have even led by 470 points with a title win.
It could be another battle for the top ranking during Indian Wells which runs from March 7 to March 20, with Djokovic currently unable to compete due to vaccination rules.