Wales manager Chris Coleman admitted fatigue had been a factor as his side lost 2-0 to Mexico in his first game in charge at the MetLife Stadium.
The Dragons were beaten by a double from Monterrey striker Aldo De Nigris, with the goals coming during the latter stages of each half.
Coleman said: "It was a tough game for us, Mexico are a super team, they play with imagination and move the ball well. They have quality in most areas. We suffered with the weather, it was hot for us but we expected that. Teams don't come much better than Mexico but we gave everything we had."
Wales failed to force Mexico goalkeeper Jesus Corona into a save, and Coleman added: "We got into good positions where maybe we could have done better but that was down to fatigue and taking the wrong option.
"We conceded the goals two minutes before the end of the first half and two minutes before the end of the game, so fatigue definitely played a part there.
"The disappointing thing was we conceded the goals from crosses, an area we would not expect to concede from. We had worked very hard at nullifying Mexico's movement but we have been caught out twice from crosses."
Coleman reserved special praise for Aberdeen goalkeeper Brown's all-round display, as he took his chance to impress with Hennessey, Boaz Myhill and Lewis Price all missing through injury.
Coleman said: "Throughout his career he has not been asked to do that and he did a great job. He is a cracking lad, a real nice guy and a good professional. He has worked very hard, he made some great saves and distributed well. Credit to him because it was difficult for him to come in at the last minute with Hennessey, Myhill and Price missing."
Mexico manager Jose Manuel de la Torre was content with his side's performance, and also paid tribute to Wales for their battling effort.
He said: ""Wales are a good team, they are very strong physically and they were able to win those aspects of the game. They made things complicated for us and the humidity and fatigue created an issue for them."