Kepa is expected to join Real next month.
"I am satisfied with our squad, which is a mix of experienced and young players," said Marcelo.
"I am not the one who makes the transfers, but Real Madrid should have the best players, and if any top player is to be signed, he is welcome."
Marcelo went on to discuss the reigning Champions League holders' upcoming fixture against Al Jazira.
"I know they are club with young players, as I know Brazilian, Romarinho, who plays for them and is a great player, but I don't know much more [about them]," he noted.
"Our experience doesn't mean anything, as always the next game will be different.
"We already know how to win and that motivates us, and I'm sure that the team will give the maximum, as they have done in all competitions."