The U.S. begin their World Cup campaign at Los Angeles Stadium in Group D, carrying the expectations that come with playing on home soil and with a squad Pochettino said has arrived in strong physical, tactical and emotional condition.
But the Argentine, who knows Paraguay well from his playing and coaching career, said Gustavo Alfaro's team would pose a serious challenge.
"I know very well the mentality, the aggressivity, the competitivity," Pochettino told reporters on Thursday.
"Paraguay showed in qualification for this World Cup how tough it is to play against them and how they performed so well. They beat Argentina, Brazil. My expectation is tomorrow is going to be a very tough game.
"They have good quality and a great coach in Gustavo Alfaro who I respect and admire him a lot."
Encouraged by recent results
Pochettino, appointed in 2024 to lead the U.S. into a home World Cup, said he was encouraged by the team's growth in the months leading into the tournament, particularly in their final two warm-up matches - a 3-2 win over Senegal and a narrow 2-1 defeat by Germany.
The coach said those performances helped convince the squad they could hold their own against leading teams.
"The last two games allowed us to think and to feel that it's possible to do whatever we want and compete in our best way, and to compete with big teams," he said.
Pochettino said the team had improved not only tactically but also mentally, adding that the players had embraced a more demanding culture around the national team.
"I think they are much better players. The mindset is starting to change," he said.
Lineup questions
Pochettino said all 26 players were available for selection, including defender Chris Richards, who had been working his way back from an ankle injury.
One decision Pochettino has already made is who will start in goal, though he declined to reveal whether Matt Turner or Matt Freese would get the nod.
"I decided," Pochettino said when asked about his starting lineup. "The starting 11 is there, unless something happens before the game."
Asked whether the goalkeepers had been informed, he smiled and added: "I don't know if they know, because if I tell you they know, you are going to start to call them."
FIFA World Cup 2026
The 2026 World Cup will be held from June 11th to July 19th in the United States, Canada and Mexico. The tournament will feature 48 national teams and will be played in 16 modern stadiums.
Match schedule and times | Group tables | England at the World Cup | Scotland at the World Cup | Team rosters at the World Cup | How to watch the World Cup | Predictions and odds | Which teams could be considered dark horses?
'Play with passion'
The Argentine said the U.S. must play with freedom and passion if they are to connect with home supporters and build momentum through the tournament.
"What we can do is contagious," he said. "We need to play with passion. We need to win games, so important, but play with passion and make the fans feel proud about what they are seeing on the field."
Asked how he would define success for the U.S. at the tournament, Pochettino was unequivocal.
"For me, success is win," he said. "It's win tomorrow and win after tomorrow.
"When we signed here, it's because we wanted to come here and be involved in this unique event, but with the possibility to compete well and a belief in winning."