Koeman is a legend at Barcelona, scoring 102 goals from defence.
Rafinha Alcantara is also back after missing the past two games due to a broken nose.
Bale, 27, has been out of action since November due to an ankle injury.
Arsene Wenger's current Arsenal contract will expire at the end of the season.
Vidal, 27, dislocated his right ankle in Barcelona's 6-0 win over Deportivo Alaves.
Los Blancos visit Pamplona four days before Champions League clash with Napoli.
Catalans visit Basque side three days before crucial Champions League trip to Paris.
Former Tottenham star yet to play a game since 22 November.
Bottom club Osasuna face daunting test against La Liga leaders.
Barcelona can leapfrog Real Madrid on the La Liga table with victory at Mendizorrotza.
Club chief also tells Barcelona to forget about playing the Copa del Rey final at the Santiago Bernabeu.
Fernandinho has revealed the conversation he had with Jesus before he signed for City.
Dani Carvajal returns to training ahead of Saturday's trip to Osasuna.
21-year-old scored his third goal of the season in the 1-0 victory over Las Palmas on Monday night.
Enrique Cerezo also played down reports linking Antoine Griezmann with a move to Manchester United.
Catalans host Diego Simeone's side in second leg of the Copa del Rey semi-finals.
Fernando Roig is continuing to perform miracles with the 'Yellow Submarine' in La Liga.
Exclusive: Barcelona have followed Bueno's progress for two years before completing a deal last week.
Neymar is suspended but Luis Enrique could recover Andres Iniesta, Sergio Busquets and Lucas Digne.
Catalans host Athletic Bilbao on Saturday following 1-1 draw at Real Betis.
Catalans host Basque side before Tuesday's Copa del Rey semi-final with Atletico Madrid.
The Spaniard would received around €30m-a-year in salary.