That was on the condition that he would get a shot at the unbeaten 36-year-old later this year, but no such assurances were given.
Instead, he will now headline his own bill, likely to be staged at the Alamodome in San Antonio, Texas.
"It is done, it is done," Schaefer told Boxingscene.com. "I'm happy it got done, because now we delivered another fight that fight fans wanted to be delivered. I'm really thrilled.
"All those people who say Canelo is afraid to fight someone like Austin Trout, I think they can shut up now.
"Canelo is not afraid to fight anyone. He will show the world on April 20 that he is the man at 154 and that nobody can or will beat him."
Alvarez, WBC champion, is unbeaten in 41 fights, while WBA titlist Trout has an unblemished 26-fight record.