The Slovenia international's diving effort to keep out Faycal Fajr's 77th-minute penalty and ensured Atletico left Coliseum Alfonso Perez with all three points after a 1-0 win.
Bale struck the first goal of Real's thrashing of Celta with a surging run forward and low finish.
Francisco "Isco" Alarcon, little-used defender Achraf Hakimi, and Toni Kroos added on, along with an own goal by Celta's Sergi Gomez, to ease to the big win at home. "It means that we are all ready for the final".
Next up for Los Rojiblancos is their Europa League final showdown with Marseille on Wednesday night.
Diego Costa, Antoine Griezmann and Koke were all wisely taken off in the second half to spare them any injury worries ahead of the trip to Lyon, where Atletico will look to end their season on a high against Marseille.
"I'm happy to have Oblak with us", Simeone told a news conference.
"We settled a tough game against a competitive team".
Getafe's defeat, combined with Sevilla's draw with Real Betis in the derby, means Jose Bordalas' side now can not finish in the top seven and earn a Europa League place.
Elsewhere, Samu Castillejo scored twice as Villarreal beat relegated Deportivo La Coruna 4-2 to leapfrog Betis into fifth, with Denis Cheryshev also netting a day after being recalled to the preliminary Russian World Cup squad.
Betis took the lead at home to fierce rivals Sevilla when defender Marc Bartra headed home from a free kick but the visiting side, who beat Real Madrid 3-2 on Wednesday, turned things around after the break with goals from Wissam ben Yedder and Simon Kjaer.
"It has been fantastic, I'd say a bit too much, but I am very grateful to the club for this detail", Prieto said.