He said Utley, who is sidelined because of a chronically injured left knee, continues to rehab in Phoenix. He is expected to rejoin the team next week, when the Phillies travel to Arizona to play the D-backs.
"His strength seems to be improving," Amaro said. "He's moving forward."
There is no timetable for Utley's return.
Martinez has a fractured right foot. He will be in a walking boot for another two weeks, when team physician Michael Ciccotti will evaluate him. De Fratus, who is rehabbing from a sprained right elbow, could pitch in an extended spring training game Thursday. He could begin a rehab assignment shortly after that.
"He's making very good progress," Amaro said of De Fratus.