The Houston Dynamo defeated Inter Miami 2-1 to win the U.S. Open Cup on Wednesday with an injured Lionel Messi watching from the stands at DRV PNK Stadium.

Without Messi and his former Barcelona team-mate Jordi Alba, Miami struggled to compete with an enterprising Houston and could have little to complain about the outcome.

Miami co-owner David Beckham, who watched the game with his former Real Madrid team-mate Zinedine Zidane, had hoped for another night of celebration after the team's Leagues Cup triumph last month.

But Miami lacked intensity and ideas as they were given the runaround by Ben Olsen's impressive Houston team.

No clear explanation has been given for Messi's injury with references to "muscle fatigue" followed by talk from coach Gerardo Martino of "scars" from an old injury.

"It was not prudent for him to play, we couldn't even consider playing him for a few minutes because we would be taking risks," said Martino after the match.

The former Barcelona and Argentina coach said he expected Messi to feature at some stage in the upcoming five games that remain for Miami in the MLS regular season.

"He will certainly play before the league is over. We will go match by match and see how things are coming along and if the medical department can give him the OK to play without any risks," he added.

Martino meanwhile said Miami's season was finally starting to catch up with them.

"I thought it was a very exhausted team, that's the reality," he said. "The reality is that we were going to feel the consequences of so many games."

With no Messi to worry about, Houston were on top from the outset, moving the ball around with confidence and purpose while Miami struggled to get a foothold.

Drake Callender was forced into a double save when Nelson Quinones drove towards the far post, the Miami keeper pushing the ball out and then doing well to get his legs to the follow up from Corey Bair.

But Houston grabbed the lead in the 24th minute with a perfect counter-attack ending with Brazilian Artur feeding the overlapping Griffin Dorsey who blasted in at the near post.

Houston were utterly dominant, passing the ball with a swiftness that left Miami chasing shadows and it wasn't long before they had doubled their advantage.

Colombian winger Quinones cut into the box from the left flank and Miami right-back DeAndre Yedlin's desperate lunge brought him crashing to the ground. French forward Amine Bassi made no mistake from the spot to make it 2-0.

Martino made two changes at the break, bringing on Venezuelan striker Josef Martinez and Ecuadorean midfielder Dixon Arroyo.

Martinez had a chance to get Miami back into the game in the 56th minute, heading wide from a good position before Benjamin Cremaschi forced Dynamo keeper Andrew Tarbell into a low save.

But as Inter pushed forward in search of a goal, Houston broke away and looked to have finished the contest off when Quinones scored after being set up by Bassi but the effort was ruled out for offside after a VAR review.

Martinez gave Miami some late hope with a left-foot strike in stoppage time after latching on to a ball from Argentine Facundo Farias.

But it was too little, too late from Miami and Houston deservedly won their second U.S. Open Cup to add to their triumph in 2018.

Miami had won the Leagues Cup last month with Messi prominently involved but they must now battle to make the Major League Soccer play-offs with uncertainty over their Argentine star's fitness.

Houston coach Ben Olsen said his team had exploited the absence of Messi and Alba.

"We prepared all week for Messi and Alba and let's be honest they are a different team (with them). I think they missed him and they missed Alba," he said.