Liverpool have offered the 27-year old a new contract, but earlier this month Crouch said he would decide on his future at the end of the season.
Crouch's team-mate, Kewell, will leave in the summer after the Australian reportedly rejected a new deal on reduced wages.
The 29-year-old winger's Liverpool career has been plagued by injury. He has made just 81 league appearances since his transfer from Leeds United in 2003.
"We have tried to come to an agreement with the player and his agent, but that has not been possible," said Benitez.
"Kewell will leave the club at the end of his contract."
And Benitez told BBC Radio Merseyside he believes injuries have prevented Kewell from fulfilling his potential at the club.
"In terms of the player he has quality. He has everything for being successful. The quality and the potential," he said.
John Arne Riise's future at Anfield looks uncertain after Benitez admitted he would listen to offers for the left-back, who has a year remaining on his current contract.
"He is not playing at the moment but he knows that if we receive an offer that is good for him and good for us, okay, we will talk," said the Spaniard.
"But at this moment he is our player. I am really pleased with him because he is a fantastic professional."
Benitez added that he had "some names to consider" before replacing Miller, who is leaving the club to manage JEF United Chiba in Japan.
