Manchester City and England midfielder Jill Scott was sent off for a headbutt in her side's 1-0 defeat by Arsenal in Women's Super League 1.
Arsenal took the lead in the 36th minute when Chioma Ubogagu slipped the ball under keeper Alex Brooks.
Scott was shown a straight red after the break after reacting to a challenge from Gunners defender Jade Bailey.
Arsenal forward Lianne Sanderson had a shot cleared off the line before City's Nikita Parris struck the post late on.
Manchester City manager Nick Cushing told BBC Sport:
"I thought we started the second half well and it looked like were really pushing (for an equaliser), but we scored an own goal with the red card.
"I'm really disappointed to have Jill off.
"We want people to come and watch and then want to come back, and these sorts of incidents go against that."
Manchester City: Brooks, McManus, Bronze (Lipman 90), Radtke, Stokes, Beattie, Scott, Christiansen, Harding (Flint 64), Duggan, Parris.
Arsenal: Byrne, Scott, Williamson, Rose, Mitchell, Bailey (Weir 88), Smith (Sanderson 46), Carter, Losada, Ubogagu (Yankey 80), Sanchon.