The U.S. moved on the gold-medal game at the London Olympics with a 4-3 extra-time win over Canada on Monday, overcoming a hat trick by Canadian captain Christine Sinclair.
But Herdman was livid with Norwegian referee Christiana Pedersen for a pair of calls that led to the third American goal. With Canada leading 3-2, Pedersen awarded the Americans an indirect free kick right outside the Canadian box after penalizing goaltender Erin McLeod for holding the ball for more than six seconds.
On the ensuing kick, Pedersen charged Marie-Eve Nault with a handball in the penalty area, and Abby Wambach converted the penalty to tie the game 3-3 with about 10 minutes left.
Herdman said "it felt like it was America and the referee against" the Canadians.
"She'll have to sleep in bed tonight after watching the replays, she's got that to live with," he said "We'll move on from this, I wonder if she'll be able to."
Canada hasn't defeated the U.S. since 2001, and Sinclair says this loss particularly stings because of the officiating.
"We feel like we didn't lose, we feel like it was taken from us," Sinclair said. "It's a shame in a game like that that was so important, the ref decided the result before it started."
Canada will play France for the bronze medal on Thursday, while the U.S. takes on Japan for gold.
It was a disappointing day for Canada in women's boxing as well. Three-time world champion Mary Spencer from Wiarton, Ont., never really challenged in her quarter-final bout, losing 17-14 to China's Jinzi Li.
Li opened up the fight by taking a lead after the second of four rounds.
"She got that lead and it was hard to get it back," Spencer said.
Off the field, there was a doping scandal as defending Olympic 50K race walk champion Alex Schwazer was caught doping in Italy and will miss the Games.
The Italian Olympic Committee said Monday that Schwazer tested positive for doping and has been removed from the team.
Committee president Gianni Petrucci said Schwazer had admitted to doping on what was a "bitter day" for Italian sports.
The 27-year-old Schwazer had been due to defend his 2008 Olympic title in the 50-kilometre walk on Saturday. Schwazer won gold at the Beijing Games in an Olympic record time of three hours 37 minutes nine seconds.
Schwazer's profile has been raised in Italy because his girlfriend, Carolina Kostner, is the reigning women's figure skating world champion.
Officials and athletes weren't the only ones getting in hot water on Day 10 of the London Games. An Olympic spectator accused of hurling a plastic bottle onto the stadium track seconds before the men's 100-metre final pleaded not guilty to creating a public nuisance.
Ashley Gill-Webb was also charged with using threatening words, disorderly behaviour and harassment.
As he left the court, Gill-Webb — who wore a grey hooded jacket and had an asthma inhaler in his mouth — shouted abuse at waiting reporters.
Sunday's race, won by Jamaican sprinter Usain Bolt, was not disrupted.