[3] Born in Torrent, Valencian Community,[4] Guaita graduated from the Valencia youth system after arriving there from CD Monte-sión at the age of 13,[5][4] being promoted to the first team for the 2008–09 season following the retirement of longtime incumbent Santiago Cañizares.

[8] However, after the signing of veteran César Sánchez from Tottenham Hotspur later in the year and the full recovery of Renan, he remained third choice until the end of the campaign.

[9][10] In 2009–10, with Sánchez having renewed his link a further year and the signing of Mallorca's Miguel Ángel Moyá, Guaita was deemed surplus to requirements and joined, on loan, Segunda División's Recreativo de Huelva.

[12] In November–December 2010, profiting from injuries to both César and Moyà, Guaita had a run of several matches for Valencia, notably a 2–1 home win against Almería in La Liga[13] and a 1–1 draw away to Manchester United in the UEFA Champions League.

[14] On 2 April 2011, as he had established himself in the starting XI, he suffered the loss of his father due to a heart attack (aged only 46),[15] prompting manager Emery to reinstate César between the posts for two games.