San Diego rallied to earn a point against visiting Boston in WUSA play Sunday night, but the Spirit lost U.S. national team star Shannon MacMillan, most likely for the season, to a knee injury sustained in the opening minutes.

MacMillan fell to a heap in the eighth minute, just seconds after Dagny Mellgren fired Boston ahead, the cleats in her right shoe snagging on the turf as she stretched with her left leg for a bouncing ball on the left wing.

She said she heard the tell-tale pop, and Spirit coach Omid Namazi and other team officials speculated that she had torn the anterior cruciate ligament in her right knee, an injury that most likely will force her to miss the Women's World Cup next fall.

MacMillan is scheduled to undergo a magnetic resonance imaging test Monday morning to determine the scale of her injury.

''I'm in immense pain right now,'' she said after the match. ''I've never felt pain like this.''

She said the thought she might miss the World Cup crossed her mind while being transported to the Spirit's training room at Torero Stadium after suffering the injury. ''All I could think was, ''World Cup is only 120-some-odd days away. What is this going to mean?' ''

MacMillan's injury marred a strong performance by a Spirit squad missing starting forwards Julie Fleeting (playing for Scotland in a European Championship qualifier) and Christine Latham (home in Calgary following her father's death).

Boston went ahead after Joy Fawcett made an uncharacteristic error, giving the ball away to Maren Meinert, who quickly played a short ball into space as Mellgren sprinted behind Fawcett. Mellgren chipped goalkeeper Jaime Pagliarulo for the goal, her fourth of the season.

Meinert's assist gave her a share of the WUSA scoring lead with Atlanta's Maribel Dominguez. Both have six goals and two assists for 14 points.

Allie Sullivan scored the tying goal in the 50th minute. Aly Wagner's free kick from the right flank was headed out of the 6-yard box by Kate Sobrero. Sullivan, on the left side of the Boston box, retreated to the rolling ball, turned, and fired with her right foot, a sharp shot across the goalmouth and into the far-side netting.

SUNDAY'S SUMMARY

May 18 at San Diego

San Diego 1 Boston 1. Goal: Sullivan 50; Mellgren (Meinert) 8.

San Diego — Pagliarulo; Pickup, Fawcett, Krzykowski; Foudy (Fair, 71), Daniela, Wagner, Connors (Nielsen, 59); Sullivan, Zhang, MacMillan (Bush, 11).

Boston — LeBlanc; Kluegel, Sobrero, Gonzalez, Aldama; Mugneret-Beghe (O'Grady, 32), Popper, Hucles (McDowell, 53), Lilly; Meinert, Mellgren (Gulbrandsen, 57).

Yellow cards — Boston: Meinert 25, Gonzalez 50.

Referee — Misail Tsapos.

A — 5,128.

WUSA STANDINGS

Pl W-L-T Pts (GF-GA)
1. Washington 6 4-1-1 13 points (14-9)
2. Atlanta 6 3-1-2 11 (14-3)
3. Boston 7 3-2-2 11 (12-14)
4. San Diego 6 2-1-3 9 (8-6)
5. San Jose 6 3-3-0 9 (6-7)
6. New York 7 3-4-0 9 (13-18)
7. Carolina 5 1-4-0 3 (9-13)
8. Philadelphia 5 1-4-0 3 (8-14)

THIS WEEK'S GAMES
Saturday, May 17
New York 1 Philadelphia 2
Washington 2 Carolina 5
Atlanta 1 San Jose 0

Sunday, May 18
San Diego 1 Boston 1

NEXT WEEK'S GAMES
Saturday, May 24
San Diego at Carolina, 4 p.m. (PAX TV)
Washington at New York, 7 p.m.
San Jose at Philadelphia, 7 p.m.

Sunday, May 25
Atlanta at Boston, 7 p.m.

All times Eastern

LEADING SCORERS

G-A–Pts
1. Maribel Dominguez (Atlanta) 6-2–14
Maren Meinert (Boston) 6-2–14
3. Mia Hamm (Washington) 4-3–11
Danielle Fotopoulos (Carolina) 3-5–11
5. Dagny Mellgren (Boston) 4-1–9
6. Julie Fleeting (San Diego) 4-0–8
Tiffeny Milbrett (New York) 3-2–8
Abby Wambach (Washington) 4-0–8
Christie Welsh (New York) 4-0–8
10. Jacqui Little (Washington) 2-3–7
Marinette Pichon (Philadelphia) 3-1–7
Birgit Prinz (Carolina) 3-1–7
13. Abby Crumpton (Atlanta) 2-2–6
Charmaine Hooper (Atlanta) 1-4–6
15. Kelly Golebiowski (Washington) 2-1–5
Shannon MacMillan (San Diego) 1-3–5
Joanne Peters (New York) 2-1–5
Homare Sawa (Atlanta) 2-1–5
Sissi (San Jose) 1-3–5
20. Shannon Boxx (New York) 0-4–4
Krista Davey (New York) 2-0–4
Monica Gonzalez (Boston) 1-2–4
Melanie Hoffmann (Philadelphia) 1-2–4
Katia (San Jose) 1-2–4
Birgit Prinz (Carolina) 2-0–4
Stacey Tullock (Philadelphia) 1-2–4