Richards had surgery after tearing a tendon in his left knee while covering first base in a game at Boston on Aug. 20. He was 13-4 with a 2.61 ERA last season.
"I think the prognosis of having him back somewhere in the first month to maybe the first six weeks of the season looks very good," Scioscia said.
Angels general manager Jerry Dipoto took a slightly different approach than his manager, calling Scioscia cautious.
"Mike is preparing for the worst-case scenario, which is more his nature," Dipoto said, according to the Los Angeles Times. "We understood it would be a six- to nine-month [recovery]. Mike sleeps better at night planning for it to be the latter of the two. We believe Garrett will be back if not on Opening Day, then at some point in the not-too-distant future."
Richards said earlier this offseason that even though his year ended early, he felt good about what he accomplished.
"It was a great season," he said. "I've learned a lot and I took a lot of positives from it. Even the games I didn't particularly pitch well, I took positives from it and made some major strides with my mentality and my delivery. It was another year where I felt like I made some major strides."
The Associated Press contributed to this report.