After winning gold at the Pan American Games in October, she pulled off a huge win at the national championships in January. Everything seemed to be on track.
But the three-time world champion was due for a slump and it happened at the worst possible time.
Spencer suffered two significant losses in the leadup to the Summer Olympics and delivered a tepid performance when she finally got to the big stage, dropping a 17-14 quarter-final decision to China's Li Jinzi on Monday.
It was a surprising result since Spencer beat Li in their two previous meetings and a win would have guaranteed her a medal.
"You win some and you lose some," said Spencer's longtime coach Charlie Stewart. "It's just when you lose them that it counts the most."
One of the most prominent faces of the Canadian Olympic team, Spencer was considered a top medal contender in London.
But she has been struggling since April, when she was trounced by American Claressa Shields. That was followed a few weeks later by a loss to Sweden's Anna Laurell at the Olympic qualifier.
That result meant Spencer needed to get a wild-card spot from the IOC's Tripartite Commission just to get to the Games.
"The last three tournaments I've been upset," Spencer said. "I don't want to pass any blame or anything. I don't want to do that but at the same time, I had the biggest victory of my life in January. To come off that and get ready for something like the Olympics, I knew it was going to be tough.
"I'm not saying I thought it was going to be easy. But it was tougher than I thought."
Spencer turned in a solid first round against Li but was flat the rest of the way. The speed, power and lightning-quick jab that she's known for were muted by an opponent who forced the Canadian to change tactics.
Li's swarming, physical strategy paid off as she effectively mixed haymakers with some clutching and grabbing.
"She got that lead and it was hard to get it back," Spencer said.
The raucous, near-capacity crowd was cheering her on but Spencer couldn't find her rhythm, landing a few punches early but looking rather ordinary throughout the four-round bout.
"All she needed were nice long straight punches (to) keep her away because she's got the height and reach advantage," Stewart said. "But it didn't happen."
Spencer, a native of Wiarton, Ont., who lives in Windsor, made mistakes that Li jumped on.
"In Olympic boxing if you don't have your hands up, you're giving free points," said Canadian team coach Sylvain Gagnon. "You can't win the fight like that."
The bout was still close until the end, in part because Li was given a two-point penalty in the fourth round. The Chinese fighter was the aggressor in the final minutes and connected on some late combinations.
"I didn't expect that kind of pressure on me," Spencer said. "I expected more jabbing. But I have to adjust. It's my fault for not adjusting."
It seemed like the loss hadn't really sunk in when Spencer spoke to reporters after the fight. She appeared disappointed but not distraught — almost like it was just a bad day at the office.
"I don't have an excuse for losing," she said. "We went in there, it was fair and we were both given the same opportunities. She came out the better boxer today.
"No reason for losing — she just had a phenomenal fight and props to her."
Later Monday, super heavyweight Simon Kean of Trois-Rivieres, Que., lost 20-6 to Ivan Dychko of Kazakhstan in a men's quarter-final bout.
Over the last year, Spencer has been thrust into the spotlight. A major player in the Canadian Olympic Committee's ad campaign, she was also featured in a CoverGirl commercial.
Stewart said the heightened media attention may have helped her in some ways and hampered her in others. Still, Spencer's coaching team felt her preparation and sparring sessions in the leadup to the Games went well.
Stewart did point out the five-foot-11 fighter had some rare pre-fight jitters.
"She doesn't normally tell me that she's nervous or anything like that but she did tell me this time that she was nervous," he said. "But listen, everybody's like that."
It would be challenging to keep the butterflies at bay considering the electric atmosphere at ExCeL London's South Arena 2. It's the official debut of women's boxing at the Games and the 10,000 fans who jammed the venue were ready for action.
The low ceiling and stuffy conditions made the arena feel like a hot yoga studio. Spencer's blue bandanna already looked damp when she walked to the ring as Blur's "Song 2" blared through the speakers.
She had received a first-round bye in the 75-kilogram category and came out scrapping in the first round. Spencer finished with a flurry and used a few combinations to stagger Li back to the corner in the dying seconds.
It was downhill from there.
Spencer took the opening round 3-2 but Li outscored her 5-2 in the second. The third round was split 3-3 and Li took the finale 7-6 for the three-point win.
The Chinese fighter moved in tight when she needed to and connected with some big right hands.
"You have to be prepared for anybody," Spencer said. "Some people are going to fight like that. That's not the first person I saw do that this tournament. So that was my fault for not being prepared for that situation."
She added that she didn't feel that the pressure and buildup over the last year affected her performance.
"To be honest, it's not like I had intentions of just coming here and giving it a shot and seeing what happened. I came here and I wanted to win gold," Spencer said. "Having a bunch of other people who are like, 'Yeah OK, you can definitely go there and medal.' That's not pressure if I already told myself that that's what I expect.
"It's different if it was the other way around."
The depth of the 75-kilogram category was obvious as the fighters looked strong in the other quarter-final bouts. Spencer said the competition keeps getting tougher.
"From my very first tournament, it's been competitive," she said. "Now it's on a world stage and people get to see a lot of upsets and they realize that any given day, anyone can win."
The first Olympic cycle proved to be a learning experience for the 27-year-old fighter.
"I guess it's the first time that's ever happened to me, where I had to be my best and then six months later I had to be better than my best," she said. "I thought I could pull it off and that I could manage it."
Li will next meet Russia's Nadezda Torlopova while Kazakhstan's Marina Volnova will face Shields in the other semifinal Wednesday. The winners will meet for gold Thursday while the losers will each receive a bronze.
Spencer will be 31 when the 2016 Summer Games are held in Rio. Her Olympic debut may have been a loss but that doesn't mean she's going to quit.
"I love this," she said. "I love boxing and I still want a gold medal."
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