Mishneh Torah — Transmission of the Oral Law מסירת תורה שבעל פה, Chapter 17

אַף עַל פִּי שֶׁאֵלּוּ הָאַחַד עָשָׂר קִבְּלוּ מֵרַבֵּנוּ הַקָּדוֹשׁ וְעָמְדוּ בְּמִדְרָשׁוֹ, רִבִּי יוֹחָנָן קָטָן הָיָה וְאַחַר כָּךְ הָיָה תַּלְמִיד לְרִבִּי יַנַּאי וְקִבַּל מִמֶּנּוּ תּוֹרָה. וְכֵן רָב קִבַּל מֵרִבִּי יַנַּאי; וּשְׁמוּאֵל קִבַּל מֵרִבִּי חֲנַנְיָה בֶּן חָמָא.

Even though all of the eleven sages mentioned above received the tradition from Rabbenu Hakadosh and attended his study sessions, [there are differences between them. At that time,] Rabbi Yochanan was of lesser stature. Afterwards, he became a disciple of Rabbi Yannai and received instruction from him. Similarly, Rav received the tradition from Rabbi Yannai, and Shemuel received the tradition from Rabbi Chanina ben Chama. to Babylonia.