Question:  Can a Muftarid (مفترض) (who offers Fard prayer) pray behind Mutanaffil (متنفل) (who offers Nafl prayer)?

Answer: (1) According to Imam Shafi’e r.a the Fard prayer offeror can pray behind the one who is praying Nafl Salah.

(2) On the contrary to above, Imam Malik and Imam Abu Hanifa r.a holds the opinion that one should not follow some one in Nafl Salah while he himself is offering Fard Salah. Therefore, we can conclude that Its best not to offer Fard prayer behind any one who is offering Nafl Salah.

Reference: [1] Sahih al-Bukhari, hadith no-722

It is mentioned in the hadith that the sayings of Prophet s.a.w  “Imam is responsible” so Mutanaffil cannot be ضامن (responsible) for Muftarid.

Reference: [1] Sahih Muslim no-414

Also this act is against the logical sense, that a strongest cannot be dependent on weakest one.