Fans of the US women’s team are unusually on edge as their crunch World Cup game against Portugal looms. Some are even thinking the unthinkable.

“I think I gained about 13,000 more grey hairs from this last match,” says fan Chris Lawler as he reflects in Auckland.

Its not the sentiment that usually accompanies the side. This team has dominated international women’s football over the past decade and have developed a fearsome aura.

The reigning champions, they have won two World Cups in a row and are the hot favourites for a record third. But a series of lacklustre performances so far has fans like Lawler on edge.

The football fan who sports a blue-dyed, Megan Rapinoe hairstyle says that following this USA team can be nerve wracking despite the rewards.

This generational side has so far struggled to gel as a unit and play homogenously. They beat debutants Vietnam 3-0 and drew one all against the Netherlands.

Despite still being at the top of the group table, those first two performances – especially that draw with the Dutch – failed to impress. And Lawler isn’t the only one to notice.

“We’re unsatisfied with the way that we’ve played, but we know the areas that we can be better,” US star Megan Rapinoe said on Sunday. “And I think there’s some really simple fixes that we can do to put ourselves in a better position.”

Her side will have a chance to set the record straight when they play their third game against Portugal tomorrow in group E. But lose and they could be on a plane home.

But something is changing in this tournament. The fiery stars and stripes have been rather lethargic and unconvincing so far.

They are missing their experienced captains Becky Sauerbrunn, forward Mallory Swanson and midfielder Sam Mewis through injury.

The team now boasts veterans like Rapinoe and Alex Morgan and debutants including young forwards Alyssa Thompson, 18, Trinity Rodman, 21, and Sophia Smith, who was last year’s most valuable player of the National Women’s Soccer league (NWSL).

Veteran superstar Rapinoe has acknowledged that her team has yet to live up to its own hype in this tournament.

“It’s a pressure moment, and that’s what the tournament is now. Every single game from here on out is that pressure moment and that’s the best part of being at the World Cup,” she said on Sunday.

The USA are now level on four points with the Dutch and are currently top of the table on goal differences. But a big win for the Netherlands against Vietnam could see the Americans bumped to second place.

All of this has made the game against Portugal more pivotal and edgy than any USA fan would have liked it to be.

“I hope they get momentum. I hope they get scared and hungry. And that we can take the next game and go into the next stage in a much better position,” said Ann Mastrota, who travelled with her daughter Katy from Washington DC.

US head coach Vlatko Andonovski said in a news conference today that the Portugal match “will absolutely not be a walk in the park”.

“They are a great team, they are very well coached, they are disciplined, organised,” he said. “We are so focused on this game and making sure we get a favourable result.”

Sports Journalist Jeff Kassouf said that while the USA are still favourites to win, they haven’t looked their dominant selves on the pitch.

“They’re a team that is used to being on top of the world,” he said.

“(But) they’re a team that is wobbling a bit. World Cups are all about timing. The timing for them is consistent injuries, unsure line up situations and it’s made them very beatable. I don’t think anybody is scared of them right now.”

There’ve been many upsets in this tournament. From Colombia beating twice world champions Germany 2-1, Japan thrashing Spain 3-nil, to Nigeria stunning co-hosts Australia 3-2.

Teams are getting better and nothing can be taken for granted, not even a US win.

“The rest of the world is catching up and this world cup is going to be lot more competitive than the past years,” Michelle Tropeano, who travelled from New Jersey said. She tells the BBC she’s hoping the team will up their game.

“I hope we fire on all cylinders for the full 90 minutes and not just 45.”

Winning this match against Portugal is not just about the US securing their position in the knockout stages.

It’s also about them reassuring their fans and themselves that they’re still deserving of their formidable status.