Solari admits the pair are now in the veteran status.
"They are very intelligent football players and, alongside Casemiro, they built one of the best midfields in Real Madrid history," he said.
"When they are at the top of their game, they are just the best.
"The truth is that they are not getting any younger, they're not in their early 20s.
"It's normal that the club might be thinking about reinforcing the midfield with another player."