Los Blancos won their opening six competitive matches of the new season but have now drawn their last four games in all competitions, a slump that coincides with the fractured leg suffered by Casemiro during the team's last victory.
Next up for the reigning European champions is a trip to the Benito Villamarín to take on Real Betis on Saturday night, and Poyet, the Andalusians' boss, believes Zinedine Zidane's side are missing the Brazil international.
Poyet told the Independent: "People say four months ago Zidane was a better coach - no. Zidane four months ago found the solution to Madrid's problems by playing Casemiro and he won the Champions League. Casemiro gets injured and now they say he is a disaster."
Betis have failed to win any of their last five meetings with Real Madrid although they did secure a 1-1 draw when the two sides last met in Andalusia in January.