The Spain international goalkeeper, who has won five La Liga titles and two UEFA Champions Leagues during his 14 years with the club, was mostly second choice under Jose Mourinho last season.
He was also a substitute in Carlo Ancelotti's first competitive match in charge of Real, a 2-1 win over Real Betis on Sunday.
However, even though Diego Lopez appears to have established himself as the club's number one keeper, Real legend Raul believes Casillas can fight his way back into the team.
"Iker is a great professional and team-mate and is experiencing something new," the 36-year-old told the club's official website.
"But with hard work and effort he will be back helping Real Madrid to achieve their objectives."
Raul - who made 741 appearances for Real, scoring 323 goals - played in a friendly against the Spanish giants for current club Al Sadd on Thursday, featuring for each side and scoring for his former team in a 5-0 win.
He was also quizzed on the future of Cristiano Ronaldo, with the Portugal international yet to sign a new deal with Real.
Ronaldo has been linked with a return to former club Manchester United, but Raul is confident he will remain in the Spanish capital.
"Cristiano is the present and future of Real Madrid, and I’m sure he’ll continue to be so," he added.
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