It seemed a touch card-happy but in truth Hercules were lucky not to have been reduced to nine by that point, as former Tottenham and Portsmouth defender Noe Pamarot escaped a second yellow for a cynical tug on Nilmar while Drenthe should have been sent straight off for a knee-high tackle on Marcos Senna, who came off soon afterwards.
Villarreal sensed an opportunity and, from the start of the second half, dominated the play.
Calatayud made excellent stops from a Nilmar chip and a Rossi header before Valero pounced on a loose ball in the box to drill a low finish into the bottom left from an angle.
It was only just after the hour mark but Hercules were hanging on as Villarreal lay camp on the edge of their penalty area, although there was a chance for a third on the counter when Thiago Gomes failed to pass to the unmarked Drenthe before firing well wide.
The hosts had another chance on the break, fashioned by the livewire Drenthe, who raced clear from halfway but was denied by a superb stop from Diego Lopez.
Cazorla had a sighter with 13 minutes left, curling just wide as Juan Carlos Garrido’s side pushed for a winner.
But they were leaving gaps at the back as shown when Pamarot almost connected with a diving header, Lopez well placed to claim.
The game was as open as it had been but Villarreal lost two men in quick succession as the red mist descended.
First Valero - who was lucky to be on the pitch after his first-half exploits - was harshly adjudged to have deliberately handled on 81 minutes, and two minutes later last-man Musacchio received his marching orders after tangling with Drenthe just inside the Villarreal half.
It was Villarreal’s turn to hang on, as Lopez made consecutive injury-time saves from a Drenthe free-kick and an Abraham Paz header.
But Hercules could not exploit 10 minutes with a one-man advantage and the spoils were shared in Alicante.