Tasmania captain George Bailey struck his maiden first class double century to effectively bat Sheffield Shield final aspirants NSW out of the game on Monday.
NSW ended day three at North Dalton Park in Wollongong at 1-141 in their second innings, still 96 runs in arrears of the competition cellar-dwellers.
Bailey, who started the day on 93, cracked 200 not out in a 389-ball knock which included 14 fours.
Bailey shared a stunning 215-run partnership with paceman Simon Milenko for the seventh wicket, in a stand which effectively locked NSW out of a game they need to win.
Milenko also hit his highest score with the former Queenslander passing a previous best of 75, only to fall on 87 within sight of a maiden century.
NSW spinner Will Somerville ran through the tail following the dismissal of Milenko to collect 5-99, with Bailey reaching his landmark before the final two wickets fell without a run added.
NSW, who need a win to maintain their hold on second, made a strong reply in the final session with opener Daniel Hughes impressing with an unbeaten 71.
First innings century-maker Ed Cowan is also unbeaten on 51.
