Heinrichs, the U.S. women's national team coach, released 10 players -- including MacMillan and three other 2002 Women's World Cup veterans -- from the Olympic Residency in Carson, Calif., as the team departed for Nashville, Tenn., where on Saturday it will face Canada in a friendly.
Among the players making the cut were goalkeeper Kristin Luckenbill, who will serve as Briana Scurry's backup, and midfielder Lorrie Fair, who returned to the team in early June after failing to make the World Cup roster last summer.
University of North Carolina stars Lindsay Tarpley and Heather O'Reilly and defender Heather Mitts, who has emerged this year as a top defender for the U.S. women, also made the 20-player roster.
The remaining 15 players are World Cup veterans whose places on the squad, for the most part, were not considered to be in jeopardy. The only player among them who appeared to be on the bubble was midfielder Angela Hucles, who is coming off strong performances in the WUSA Soccer Festivals the past two weekends in Blaine, Minn., and Carson.
Heinrichs will announce the Olympic roster during a teleconference on Thursday.
MacMillan, 29, who played in the 1996 and 2000 Olympics and in the 1999 and 2003 World Cups, has never recovered the form she displayed before suffering a torn anterior cruciate ligament during the 2003 WUSA season. She made what was called a ''miraculous'' return to the U.S. roster for the World Cup last fall.
MacMillan has scored 60 goals in 171 appearances with the U.S. women, but she has seen action in just one match -- 19 minutes in a 1-1 tie against Japan on June 4 -- since the Residency began in early April.
Goalkeeper Siri Mullinix and defenders Danielle Slaton and Kylie Bivens, all on the World Cup team, also were released Wednesday.
Mullinix, the 2000 Olympics starter, has been slowed by a shoulder injury. Slaton has been playing with longstanding knee problems. Bivens was odd woman out from the Americans' deep backline.
A fifth World Cup player, Tiffeny Milbrett, in December turned down an invitation to continue playing with the U.S. team in a conflict with Heinrichs over playing style and system.
Also released Wednesday were goalkeeper Jenni Branam, defender Amy LePeilbet, midfielders Lori Chalupny, Lori Lindsey and Leslie Osborne, and forward Christie Welsh.
All of the released players remain in the running for one of four U.S. Olympic alternates, to be chosen late in July, and Mullinix is the likely alternate in the nets. All except Chalupny, who will be a junior at the University of North Carolina next fall, continue to be paid under terms of the Residency contract.
Fair received a Residency contract this week following two weeks in camp as a ''guest'' player. Luckenbill, Welsh and Lindsey earlier received contracts after two-week trials.
Chalupny and Osborne, a senior at Santa Clara University, are expected to join the U.S. under-21 team for next month's Nordic Cup in Iceland.
The U.S. women are grouped with Australia, Brazil and host Greece for the first stage of the Aug. 11-26 Olympic tournament.
U.S. OLYMPIC ROSTER: FINAL 20 PLAYERS
(With current club or college affiliation or most recent college or WUSA affiliation in parentheses)
Goalkeepers 1 Briana Scurry (Atlanta Beat), 138 caps/0 goals
24 Kristin Luckenbill (Carolina Courage), 3/0
Defenders 6 Brandi Chastain (California Storm/WPSL), 177/30
14 Joy Fawcett (San Diego Spirit), 232/27
15 Kate Markgraf (Boston Breakers), 118/0
21 Heather Mitts (Philadelphia Charge), 19/0
3 Christie Rampone (New York Power), 118/4
4 Catherine Reddick (University of North Carolina), 56/4
7 Shannon Boxx (New York Power), 23/9
2 Lorrie Fair (California Storm/WPSL), 114/7
11 Julie Foudy (San Diego Spirit), 153/44
19 Angela Hucles (San Diego Spirit), 32/4
13 Kristine Lilly (Boston Breakers), 273/95
5 Tiffany Roberts (Carolina Courage), 107/7
16 Lindsay Tarpley (University of North Carolina), 23/7
10 Aly Wagner (Boston Breakers), 63/14
9 Mia Hamm (Washington Freedom), 257/149
27 Heather O'Reilly (Univ. of North Carolina and New Jersey Wildcats/W-League), 22/3
12 Cindy Parlow (Atlanta Beat), 143/69
20 Abby Wambach (New York Power), 37/26