The Sabres announced that the 19-year-old Grigorenko, who previously had said he would not accept the assignment, had changed his mind Sunday night.
Grigorenko had two goals in 18 games but last played for the Sabres on Nov. 27. He had team-highs of five goals and eight points playing with Russia at the 2014 IIHF World Junior Championship.
Due to the agreement between the NHL and the Canadian Hockey League, players drafted from a CHL team are barred from playing in the American Hockey League until age 20.
Grigorenko's agent, Jay Grossman, told The Associated Press his client agreed to report to the Remparts after lengthy discussions with Sabres president Pat LaFontaine and newly hired general manager Tim Murray.
"It's safe to say we've had serious concerns about his development process and that was warranted," Grossman told The Associated Press. "We felt it was important for the Sabres to look more carefully at his development and that we had these kinds of conversations that were necessary so that we were on the same page going forward with respect to his development."
Grossman called the discussions positive and said he was pleased to have a chance to air his concerns directly with Murray, who was hired Thursday.
"The hope is that with him being assigned outside the organization that they were going to monitor his progress," Grossman said. "I think time will tell. I think that it's obviously the player's responsibility, which he surely is willing to take on to work hard and to continue to develop his game."