Ronaldo, 35, is bidding to become only the second player to score 100 goals at international level after Iran’s Ali Daei.
Cristiano Ronaldo may have to wait a few days longer before he can attempt to score his 100th Portugal goal after a toe infection made him doubtful for Saturday's Nations League match at home to Croatia.
Ronaldo, Portugal's all-time leading scorer and most capped player, has been stuck on 99 goals for 10 months since scoring in the 2-0 win away to Luxembourg in their last international.
"I have a few doubts as to whether he will be fit," coach Fernando Santos told reporters.
"Cristiano trained very well on Monday and Tuesday but on Wednesday had this pain in his toe.
"It looked a bit like a bee sting but it turned out to be an infection. It has been treated with antibiotics and seems to be back to normal but we still have to evaluate it."
There have been no international matches played in Europe since last November due to the coronavirus pandemic, which forced the postponement of Euro 2020 until next year.
Ronaldo, 35, is bidding to become only the second player to score 100 goals at international level after Iran's Ali Daei.
Portugal's following match is away to Sweden on Tuesday.