"He's real good," Mariners manager Don Wakamatsu said.
Lee, on the 15-day disabled list with a strained lower abdominal muscle, will throw again before Sunday's game, this time for 45 pitches.
Injured left-hander Erik Bedard will also throw 45 pitches Sunday. Wakamatsu said Saturday that Bedard is also ahead of schedule, like Lee, but won't be rushed.
"It's the same scenario," Wakamatsu said. "Once we get them back, we want to keep them here."