Portugal football legend Eusebio was given the all clear on Sunday after being taken to hospital because of high blood pressure on Saturday evening after falling ill.
However, the team doctor Henrique Jones told Portuguese media that Eusebio would be able to leave hospital on Monday.
"He is stable. He was joking and speaking with us. He should be up to leaving hospital tomorrow (Monday)," said Jones.
"He will stay in hospital for an extra day as a precautionary measure.
However, Jones said that Eusebio would return to Portugal before the semi-final between Portugal and defending champions Spain in Donetsk, Ukraine, on Wednesday.
"Given the status of his heart, it is preferable that he doesn't stay for the match against Spain."