The Brits fell to a narrow 7-6 defeat against a heavily-fancied Russia in their opening London 2012 game at the Water Polo venue, but there were plenty of encouraging signs for the home side.
And former Hungary goalkeeper Fekete believes Team GB will be stronger for the experience as they chase Olympic success in home water.
He said: “Today we proved we were ready for these Games and I expect even better performances in the upcoming matches.
“All we want to prove is that this is an eight-horse race, not just seven."
All eight teams in the competition will qualify for the knockout stages but success in the group stages could set up a favourable draw for Team GB.
A Francesca Painter-Snell penalty opened the scoring with Team GB’s first ever goal in the competition, before goals from Chloe Wilcox and Angie Winstanley-Smith rewarded the crowd for their raucous support.
Fiona McCann scored a fourth before Winstanley-Smith netted again as the sides entered the half-time break tied at 5-5.
The Brits entered the final period a goal down and a Winstanley-Smith third looked set to secure a point but the Russians scored with just four minutes remaining to claim the win.
Captain Fran Leighton echoed her coach’s defiant words as they look to prove they can compete with the sport’s powerhouses, including Beijing bronze medallists Australia, who they face on Wednesday.
The 30-year-old centre forward admitted her side were unlucky against the Russians, and promised her side would be thorough in their preparations as they look to build on their solid start.
She said: “First, I need to sit down as my legs are killing, then we have a full training session in the morning as we know it's going to be tough on Wednesday.
“I'm a little tired right now, but it was a great game. We deserve to be here and it was good to be able to prove this.”
American Maggie Steffens made the most of her Olympic debut as the 19-year-old Californian scored seven goals in a 14-13 win over Hungary.
Steffens's talent and poise in front of goal stood out on a day that otherwise contained few surprises, with the favoured US and Australian squads, the 2008 Beijing Games silver and bronze medallists respectively, securing wins.
Steffens, who watched from the stands when her sister and team mate Jessica competed in Beijing four years ago, said she felt "awesome" after recording the biggest Olympic debut goal tally in the history of women's water polo at the Games.
"Was I surprised? No. She has so much potential in her and I think she's been waiting to bust out of her skin," Jessica, 25, said of her sister's performance.
The US team has the Olympic gold medal firmly in its sights, according to Maggie, who deferred her place at Stanford University in California to concentrate on water polo.
"This is more important. Stanford can wait for the possibility of a medal," Maggie, sporting red scratches on her chest after scrapping against the Hungarians in this most demanding and aggressive of sports, told reporters.
US captain Brenda Villa, 32, who is competing in her fourth Olympics, praised the younger Steffens, saying that it was not just the goals she scored but the chances she created which made her a stand-out player.
"She's a youngster but you would never tell in the water, she plays like she's being playing at this level for a long time," Villa said.
The US looked the stronger side, but came up against a tough Hungarian team which responded to every US move in a thrilling match that went down to the wire after a Hungarian goal in the final minute.
In the earlier games, Australia overcame a series of Italian retorts for a 10-8 victory, while Spain, playing in its women's Olympic water polo debut, used a series of outside shots to pound China 11-6.
The women's competition in London is considered much more open than at previous Games with defending Olympic champion Netherlands and reigning world champion Greece both absent after shock defeats in the qualification stages.
Australian coach Greg McFadden played down his team's status as one the favourites.
"I believe there's six or seven really good teams there. This is the most open Olympic games since I became involved in 2004," he said.