Miller is 10 of 11 on 3-pointers in the Finals and is shooting 50 percent from behind the arc in the postseason. He started 17 games in the regular season, mostly as a fill-in for Dwyane Wade when he was battling injuries, and the Heat were 13-4 in those games.
Miller started Game 4 of the Heat's series against the Milwaukee Bucks, and the Heat won by 11 points.
Miller will replace Udonis Haslem in the starting lineup to give the Heat more shooters in an attempt to spread the floor. The Spurs have been successful in packing the paint over the series' first three games and it has cramped the driving space for LeBron James and Wade.
That lineup started together twice in the regular season and averaged 107 points in wins over the Chicago Bulls and Boston Celtics. It has played 22 minutes together in the playoffs, outscoring the opposition by nine points in that time.
In that configuration, James can start the game as the Heat's defensive center and spend extended time guarding Tim Duncan. Haslem has been good defensively on Duncan in the series but has struggled offensively.
One of the Heat's priorities going into Game 4 is expected to be deploying more shooting lineups. That could mean reduced playing time for backup point guard Norris Cole and more for Shane Battier, who recently has been out of the rotation.
ESPN.com's Tom Haberstroh contributed to this report.