Portugal were held to a draw in their tournament opener after struggling to turn possession into clear chances. They controlled much of the match but managed only seven shots, with just one effort on target - Joao Neves's early header.
Martinez admitted his team lost control after a strong start but said the players were determined to respond.
"We are strong and focused," Martinez said. "Our group is even more united than before. It is a process. Tension is not part of our team."
The Portuguese coach added that criticism was expected after a below-par performance but insisted it would not affect the squad's preparation.
"It is normal to have criticism after a poor result. Sometimes it is unfair or negative, but it is not part of how we prepare," he said.
Portugal were expected to have almost a full squad available for the Uzbekistan clash, with only Tomas Araujo ruled out. Ruben Dias was also set to return after missing the opening game.
Martinez also defended captain Cristiano Ronaldo after questions were raised over his place in the starting line-up following his performance against Congo.
The manager highlighted Ronaldo's importance to Portugal's style of play and his experience at international level.
"We are a team that wants the ball. We want to defend and react quickly. We want to counterattack quickly," Martinez said. "You need a player that opens up space with movement and Cristiano is one of the best to do that."
"He is a player who has been defending and playing for his country for a long time and he wants to keep improving for the team. He is really a role model for the team."
With Colombia beating Uzbekistan 3-1 in their opening Group K match, Martinez admitted Portugal needed a positive result to stay in contention for a place in the knockout stages.
"The feeling of disappointment is one we all have as a team," he said. "Tomorrow I do feel like we will have a team that will be ready to perform for 90 minutes at the level we have."
