In yesterday’s Mishna (Menachot 13b) we see a dispute between Rabbi Yose ben Chalafta and the (contemporary) Sages.
שחט שני כבשים לאכול אחת מן החלות למחר הקטיר שני בזיכין לאכול אחד מן הסדרים למחר
רבי יוסי אומר אותו החלה ואותו הסדר שחישב עליו פיגול וחייבין עליו כרת והשני פסול ואין בו כרת
וחכמים אומרים זה וזה פיגול וחייבין עליו כרת:
And then, in today’s daf (Menachot 14a
) there is a brayta which records Rabbi Yehuda HaNasi’s opinion:
הא מני רבי היא
דתניא השוחט את הכבש לאכול חצי זית מחלה זו וכן חבירו לאכול חצי זית מחלה זו
רבי אומר אומר אני שזה כשר
If Rabbi has an opinion, how come he does not speak up in the Mishna he redacted? (Certainly if he differs with both. But also, if he will hold like either the Sages or like Rabbi Meir, shouldn’t he express this.)
One answer might be that he is trying to have a light touch on the Mishna, either as an earlier extant text before him, or because he wants to primarily present the dispute among the Tannaim of the previous generation, rather than the Mishna being an expression of his own views.
Rabbi as a 6th generation student of Rabbi Yose
We see from the graph that Rabbi Yose was a 5th generation Tanna, while Rabbi Yehuda HaNasi was of the subsequent generation. The Sages would be of the same generation, meaning fifth generation Tannaim.
Further, maybe this is why Rabbi often uses the expression omer ani, as he does here in the brayta. This would not just be humility. He wants to distinguish between the corpus of recorded previous-generation disputes and his own view of the matter.
(As an aside, it seems possible that Rav Huna, by saying that the brayta brought by Rav Nachman in objection was the opinion of Rabbi, is to say that Rabbi has his own opinion, which is neither that of Rabbi Yose nor of the Sages. But the setama degemara assumes that it must be in accordance with Rabbi Yose or the Sages, and asks this, despite the words omer ani.)