Casilla was displaced by Illan Meslier as Leeds number 1 towards the end of last season after the Spaniard was suspended for disciplinary reasons.
The 34-year-old has only clocked up minutes in cup competitions in the current campaign, but is yet to be on the winning side, with his latest showing in Sunday’s FA Cup exit against Crawley Town owing to a 3-0 loss putting him under increased scrutiny.
However, Bielsa insists he still has complete faith in Casilla as a player and vowed he will do whatever it takes to help him.
The Argentine is of the view that the harsh treatment received by Casilla from some fans ignores the integral role he played in Leeds’ promotion clinching Championship run last season.
Asked whether he still trusts Casilla, Bielsa told a press conference: No [I don’t feel the need to turn to Elia Caprile], I fully trust in Kiko.
“And I will do the utmost possible to help him.
“I think that the treatment Kiko has suffered ignores the fact that he is a player who played 40 games for Real Madrid.
“Apart from whether his performances were good or bad, we forget all the thing he has done to get the team promoted.
“People also don’t consider how he’s being treated publicly given the situation that he had to go through when he was suspended for eight games.
“I believe in him; his team-mates believe in him and we are close to him because we value him as a person and a footballer.
“We accept what people think of him in the media or people, but we know his past and we know his conditions and we care about him a lot as a human being.”
Casilla has made the bench in 14 of Leeds’ 17 league games so far this season, but is yet play a single minute of top flight football with Meslier getting the nod ahead of the veteran custodian.