If on the other hand, the two rabbis were already making veiled references to Reish Lakish's past (my interpretation), then Yochanan's comment is already on topic.

Poor form still, but no longer out of the blue.

This interpretation also makes Reish Lakish's response of "what good did you do me?" have more resonance with the rest of the conversation. (Although it is a sequitur in either interpretation.)