The progress of Brooklyn Nets star Ben Simmons in practices this week -- and the anticipation that it will further accelerate in the coming days -- has turned Game 4 on Monday into a realistic target for his season debut, sources told ESPN.

Simmons hasn't been ruled out for Game 3 of the first-round playoff series against the Boston Celtics, sources said, but there are still more hurdles Simmons would be required to clear in a much shorter window of time for him to be ready to play in Saturday's game in Brooklyn, sources told ESPN.

Simmons has been recovering from a herniated disk in his lower back, and has yet to play for either the Nets or the Philadelphia 76ers this season.

Boston leads Brooklyn 1-0 in the best-of-seven first-round Eastern Conference series. Game 2 is Wednesday night in Boston.

Simmons has not played in an NBA game since last May after requesting a trade from the Sixers, citing mental health concerns. He was cleared for contact Monday and has been getting in some 4-on-4 work with teammates.

Nets coach Steve Nash said Simmons would get another workout in before Wednesday's game.

Nash remained noncommittal on a timeline for any potential return for Simmons.

"There's no other way than him to say, 'I'm ready,'" Nash said after Wednesday's shootaround. "Especially after an absence this long. So whenever he is ready, it's going to have to be on him to say, 'I feel comfortable. I feel ready to go. I want to play and I want to contribute.'

"We can't push him places when you have been out this long. It's got to be something where he is definitely comfortable and ready to play."

Information from ESPN's Nick Friedell was used in this report.