Berbatov has made an impressive impact at Craven Cottage since arriving in the summer and scored another fine goal in Saturday's 3-3 draw with Reading.
Riether believes the Bulgarian has already established himself as a key figure, saying the rest of the team are doing their best to play to his strengths.
"We know that Berba's a great player and we saw that again [at Reading]," Riether told the Fulham and Hammersmith Chronicle.
"His goal was unbelievable. He can always keep the ball and he's a very important player for us.
"We saw when he was not there - when he was injured and did not play - that we did not have the player at the front who could keep the ball for us, and it's good to have him back.
"Our game is to always play to Berba's feet."