USS Potemkin

The USS Potemkin and the USS Lassiter were the two main Starfleet starships which confronted the Borg in the initial stages of the invasion of Delta IV. (COMIC: Assimilation²)

Behind the scenes
From a DWU perspective, it hardly matters that there have been several Starships Potemkin. From an STU standpoint, however, it's a matter of curiosity which Potemkin this is. It's never shown, so Star Trek fans are left to speculate based solely on the given stardate of the story. It plausibly could be the NCC-18253 or the Defiant-class vessel of the same name.