Lionel Messi's fitness remains in doubt ahead of Thursday's Copa America quarter-final with Ecuador with coach Lionel Scaloni saying he will wait before deciding on his team.

Messi missed Argentina's final group stage match on Saturday, a 2-0 win over Peru, after complaining of a sore right hamstring.

Argentina will hold a training session later on Wednesday and Scaloni said he would make any decision afterwards.

"We'll wait a couple of hours and make the decision. It is always better to have one more day," he told a press conference.

"Yesterday we had good feelings and we'll take this day to define the team based on the response we get today," he added.

Scaloni said he would consult with the 37-year-old Messi about his readiness for the game.

"We'll try to get him in and then, if he's not (ready), we'll look for the best solution for the team. I'll talk to him today. I think it's fair that he takes his time and trains as much as possible," he said.

Scaloni made nine changes against Peru as he took the chance to rotate his squad with qualification to the knockout stage already secured.

Should Messi not be ready to start against Ecuador, Scaloni could start with both Julian Alvarez and Lautaro Martinez as twin strikers in attack.

Lautaro is the top scorer in the Copa so far with four goals from three games, including a double against Peru while Alvarez found the target in the opening game against Canada.

"They have already played together against this rival. We will make the decision after today's training session. We are not ruling anything out because they have worked well and it is an option, it could be," said Scaloni.

"Lautaro is doing very well, in a good moment, the same as Julian. Lautaro has not only done well, but he has waited for his chance and that makes me very happy. They both scored goals, let's hope that streak continues tomorrow. We are satisfied with their contributions," he said.

Ecuador coach Felix Sanchez said he doesn't expect a radical change of approach from  Argentina -- with or without Messi.

"We know we are playing a high level team, Lionel Messi is the player that makes the difference and we have played against them with him and without him on the field," he said.

"Their gameplan doesn't change much - they are a group who have been with their head coach for a long time, they know their gameplan and we have had to be ready either way," added the Spaniard.