Gignac double helps Marseille delay PSG's party
"It was tough tonight but we enjoyed it," Valbuena told French TV channel Canal Plus.
"When Bastia equalised, we did not give up, that's what matters. We want that second place."
Lille's hopes of clinching a Champions League spot took a major blow when they were beaten 4-2 at Toulouse.
Marko Basa and Salomon Kalou's goals cancelled out Wissam Ben Yedder and Etienne Didot's early strikes for the hosts, only for the visitors to concede two more goals after the break.
Daniel Braaten put Toulouse in front again with some cool finishing after collecting a defence-splitting pass and substitute Eden Ben Basat put the result beyond doubt from Braaten's pass one minute from time.
Lille remain fifth on 57 points, three behind Lyon.
At the Stade Velodrome, OM got off to a brilliant start as Gignac collected Valbuena's through ball and chipped the ball past Mickael Landreau in the 12th minute.
Bastia equalised one minute into the second half when Florian Thauvin beat Steve Mandanda with a fine 25-metre shot.
Landreau tipped away Morgan Amalfitano's rising shot over the bar and denied Jordan Ayew from just inside the box as the visitors held firm.
Nine minutes from time, however, Gignac was again at the receiving end of a Valbuena long pass and fired past Landreau.
Stade Brest look almost certain to be relegated after losing 2-1 at Montpellier.
They have 29 points and lie six points from safety.
Troyes have 31 after Jean-Christophe Bahebeck's second-half goal gave them a 1-0 win against Evian Thonon Gaillard who are 18th on 34 points.
Sochaux eased their relegation fears with a 1-0 home victory against Lorient thanks to Sloan Privat's fierce strike on the half-hour mark.