The two-time UEFA Cup winners went into the break with a 1-0 advantage following Patrick Herrmann's 21st-minute strike before second-half substitute Ikechukwu Uche rescued a point for Villarreal.
Herrmann breaks deadlock
Though possession was fairly evenly-balanced, Mönchengladbach looked the more dangerous side in the first half at the Borussia Park. The first real opportunity of the contest fell to Foals left-back Oscar Wendt, who fired just wide from long range, before Villarreal's Denis Cheryshev failed to get the better of Yann Sommer in a one-on-one situation with the Swiss keeper.
Herrmann did better only moments later at the other end, however, leaving Villarreal stopper Sergio Asenjo grasping at thin air with a left-footed effort from the edge box. Boosted by that goal, the home side upped the pressure and should have doubled their lead when Braminir Hrgota missed the target from a promising position in the closing stages of the half.
Villarreal offered more as an attacking force after the break while continuing to pose a threat on the counter-attack. Alvaro Domiguez did particularly well to block Luciano Vietto inside the area, while Cheryshev sent an effort over the crossbar soon after. The guests were finally rewarded for their endeavours in the 68th minute when Uche steered Manu Trigueros pass into the net with his first touch of the match.
Gladbach showed they weren't ready to settle for a draw, however. Lucien Favre threw on Ibrahima Traore and Raffael, but clear-cut goalscoring chances remained at a premium in the final stages. Granit Xhaka came closest to breaking down a solid Villarreal defence with two shots from distance, but the Foals' had to make do with a point.
Mönchengladbach: Sommer - Jantschke, Stranzl, Alvaro Dominguez, Wendt - Kramer, Xhaka - Herrmann (74' Traore), Johnson (62' Hahn) – Hrgota (77' Raffael), M. Kruse
Villarreal: Sergio Asenjo - Mario Gaspar, Musacchio, Victor Ruiz , Gabriel Paulista - Pina (60' Trigueros), Bruno Soriano - Moises Gomez , Cani - Cheryshev - Vietto (67' Uche, 73' dos Santos)
Goals: 1-0 Herrmann (21'), 1-1 Uche (68')
Felix Seaman-Höschele reporting from the Borussia Park