say many years ago as an undergrad you took a class like Math 55 at Harvard or the equivalent at MIT/etc. ie. something with a really strong reputation.
for those not familiar:
http://www.thecrimson.com/article/2006/12/6/burden-of-proof-at-1002-am/
now, the well-known prof has agreed to write a rec, but as it states in the article, you were among the 10 who didn't understand the course. so he says the rec would not be that strong. a strong rec from this prof would probably guarantee admission ... my dilemma is whether a weak rec is worth anything.
this is for an MS in Stats program, and my other options for recommendations are very limited. any thoughts?