"He is absolutely 100 percent."
The Philadelphia Inquirer reported Lee mildly strained his side before he reported to Bright House Field for Spring Training.
"He had some soreness in the offseason, about a month ago," Amaro said. "He talked to our trainers. We brought him in. He had a mild strain of his lat. He's perfectly fine."
Asked if Lee would be ready to pitch Opening Day if asked, Amaro said, "He's on course with every other pitcher we have."
Lee's first bullpen session last week was shorter than his peers. Amaro said his bullpen sessions "have been fine since. We have been overly cautious."