This is a skills building shiur on masechet berachot. In the first semester, we covered the first three pages of the masechet. We pick up at the bottom of 4b with an analysis of the position of the Chachamim in the mishna. The gemara assumes that the Chachamim must be in line with either R. Eliezer or Rabban Gamliel from the mishna. This opening question and assumption leads to a forced read of their approach. Rashi tries diligently to make sense of the sugya.
You can find the sugya, with words to looks up as well as the parallel material in this doc.
Here is the audio from the shiur: