they officially want off the case just as his federal trial is approaching, and it means he could have some serious legal shuffling to do ...

Attorneys Steven Greenberg and Michael Leonard -- who've been with Kelly for years -- filed documents late Monday requesting to withdraw from the singer's federal case.

They tell us, "The only comment we have at this time is that Mr Kelly terminated both lawyers prior to filing their motion.".

Greenberg and Leonard tell us they want out because, in their opinions, Farinella and Becker don't have enough experience with federal criminal cases -- but they add, "We wish Mr.