Manasikara is one of the five constituents of name nama. Yoniso and ayoniso stem from from this. Yoniso is translated as radical and ayoniso as un-radical. Consciousness is the culprit of everything and it happens along with nama.
So Sati is like a watchman who does the watching. That is, Sati, when practiced correctly ensures that yoniso manasikara is maintained at all times. Sati and manasikara has to co exist for the practice to flourish.
This is my understanding please.