The Spanish national team have confirmed that Napoli midfielder has withdrawn from their latest squad due to illness.
Ruiz, 22, is yet to make his debut for La Roja's senior side, although was initially part of the squad set to begin UEFA Euro 2020 qualifying campaign this weekend against Norway, before playing their second game three days later against Malta.
As a result of the Napoli midfielder's withdrawal, which will come as a blow for him due to his fine form for the Serie A side this season, the national team have confirmed (via Twitter) that Atletico Madrid midfielder Saul Niguez has been called up to fill the void left by Ruiz.
Saul is certainly no stranger to playing for Spain, with the 24-year-old earning 15 caps for the senior team since his debut in September 2016. The Atleti star was also part of the Spanish squad during their 2018 World Cup campaign, although never featured as they crashed out at the round of 16 stage.
The upcoming international break marks Spain's first games since finishing second in their UEFA Nations League group - that England topped - as a 3-2 defeat in their final group game against Croatia cost them the chance of competing the finals of the tournament this summer.
Along with Norway and Malta, Spain have been drawn Sweden, Romania and the Faroe Islands in Group F, as Luis Enrique's target reaching the finals, and regaining a trophy they've won twice in the last three years (2008 and 2012), after Portugal won the Euros against host nation France in 2016.