In explaining Menasech the Gemara brings the explanations of Rav and of Shmuel. Rashi on Rav's explanation says: Shikshah (Rippled the wine) Byado (with his hand): he put his hand into the wine and moved his hand, and that is the way the ritual of Menasech was done in Avoda Zarah.

Rav's explanation in the Gemara is later elaborated in the Gemara, which explains that Rav's explanation of Menasech is similar to that of Rabbi Yirmiyah, who says that in lifting the wine the Menasech already beomes liable for the value of the wine, and the culpability for Menasech arisies only at the act itself, which is a later act; therefor Rav must explain that Menasech in the Mishnah where monetary liability is discussed arises by the act of Menasech and NOT before!

However- what if the Menasech did NOT have the intent of Gezelah? It seems that the Gemara here implies that he would NOT be liable for payment but only culpable for doing Avoda Zara? Perhaps since Ein Adam Osser Davar She'eino Shelo there would be no culpability at all: he didn't take possession of the wine at all, and therefore his libation was of no effect, and the wine would not become prohibited at all!

Could it be that Rashi ment to say: in lifting the wine to do the libation BY DEFINITION this is Gezela, and therefor he is liable for damages - in case he lifted the wine, but if he didn't lift the wine, but only did Shikshuch - our Mishnah says a new law: he'd be liable for damages anyway