The Serie A club is owned by Massimo Cellino, Leeds' prospective new owner who sacked manager Brian McDermott on a dramatic deadline day.
And in a first sign of a link-up between the two clubs, a statement on the Cagliari website said Tabanelli had been sent to Elland Road.
The player, who turns 24 on Sunday, moved to Cagliari only last month after spending the first half of the season with Serie B club Cesena.