After missing the last two games with a thigh injury, the Porto midfielder will join his teammates for training on Sunday for the first time since their opening win over Ghana.
Centre half Danilo Pereira, who sustained three broken ribs last week, is also recovering well and could feature later in the tournament.
His replacement in the last two matches was defender Pepe, who is likely to keep his place and be tasked with marking Swiss striker Breel Embolo, who has scored twice in the tournament.
Pepe will be paired with Manchester City centre-back Ruben Dias, who was rested for their last group match against South Korea which Portugal lost 2-1.
Santos was forced into a change at left back after Nuno Mendes was ruled out of the World Cup due to an injury suffered in the first half against Uruguay.
Santos switched Joao Cancelo to the left and brought in Diogo Dalot at right back and the coach is expected to keep the same formation against Switzerland.
Captain Cristiano Ronaldo will bid again to equal the record of World Cup goals scored for Portugal held by Eusebio, who racked up nine in 1966 in England.
Switzerland have their own forward seeking a place in the record books.
Xherdan Shaqiri's goal against Serbia in the group stage meant he has found the net in more World Cup tournaments than any other Swiss player, having also scored in 2014 and 2018.
He is one goal away from matching the most World Cup goals scored by a Switzerland player - six, by Sepp Huegi all in 1954.
The Swiss quietly finished second in their group behind Brazil, victories over Cameroon and Serbia earning their place in the last 16.
