Hayward has not played since Game 1 of the Celtics' first-round playoff series against the Philadelphia 76ers on August 17 because of an ankle injury.
Boston excelled in spite of Hayward's absence by sweeping the Sixers and then beating the reigning NBA champion Toronto Raptors in seven games in the second round, but his potential return comes at an ideal time for the Celtics.
The C's blew significant leads in both Game 1 and Game 2 of the Eastern Conference Finals, and they now trail the Heat by a 2-0 margin in the series.
Hayward struggled last season in what was his first year back after fracturing his tibia and dislocating his ankle in the first game of the 2017-18 season, but he looked more himself this season, as he averaged 17.5 points, 6.7 rebounds and 4.1 assists per game.
The former Utah Jazz star was especially good in seven regular-season games in the NBA bubble with averages of 18.7 points, 7.7 rebounds and 3.9 assists per contest.
If Hayward can play Saturday, it will give the Celtics an even deeper lineup and a complement to the likes of Jayson Tatum, Kemba Walker and Jaylen Brown.
Hayward would also give head coach Brad Stevens another option to defend Jimmy Butler, although Butler was largely held in check in Game 2 with just 14 points on 4-of-11 shooting.
The Celtics are entering do-or-die territory since a 3-0 series deficit against a quality team like Miami would be incredibly difficult to come back from.
Having all hands on deck is of the utmost importance, especially when it comes to a versatile former All-Star in Hayward who can impact the game in myriad ways.