The visitors had a composed start to the game and Antoine Griezmann went close to opening the scoring when he latched on to Mario Suarez's cross, but his header went wide of the target.
Minutes later, Diego Godin went close as he forced a save from Ruben as he powered a header at goal from Koke's corner from the right.
Atletico continued to press and Ruben was forced into action again when Guilherme Siqueira raided down the left and crossed for Raul Garcia, but his volley was beaten away by the keeper.
Diego Simeone's men almost took the lead when Griezmann worked the ball well with Tiago and the Portuguese midfielder powered a strike towards goal. However, Ruben was again alert to the danger and palmed the ball past the post with an impressive one-handed stop.
Just before the break, Ruben denied the visitors once more as Koke did well to find the run of Garcia in the box. Garcia took a touch to get the ball out of his feet then launched a powerful strike at goal, but the keeper parried the ball wide.