Valdés started his career at Santiago-based Palestino. In December 1999, he was signed by then Italian Serie A side Bari along with countryman Pascual de Gregorio. He made his Serie A debut in the next season, on 15 October 2000. He replaced Rachid Neqrouz in the 84th minute when the team was a goal down to Juventus. The matched ended in 2-0. Valdés followed the team down to Serie B after the club's June 2001 relegation and became a first-team regular in the team, replacing Antonio Cassano. In August 2004, he was signed by Serie A side ACF Fiorentina in a co-ownership deal. As part of the deal, Massimiliano Scaglia moved in the opposite direction, also in a co-ownership deal. Valdés played his first league game for La Viola on 19 December 2004, a 2–0 victory over Chievo. He replaced Javier Portillo in the 76th minute, six minutes after Portillo scored the 2nd goal. He only played 5 Serie A matches for Fiorentina in the first half of the season.
Spells at Lecce and Atalanta
In January 2005, Valeri Bojinov was transferred to ACF Fiorentina from Lecce and Fiorentina sold its 50% registration rights to Lecce as part of the deal. Lecce then bought the remain 50% rights from Bari in June 2005. He followed Lecce relegated to Serie B in June 2006. He was a regular starter in 2006-07 season, but in 2007-08 just made 14 starts in 36 Serie B appearances. After Lecce won promotion back to Serie A, he left for fellow Serie A team Atalanta on free transfer in July 2008, which the deal already agreed in January. At first he was a substitute player but gained a regular place in November 2008. He scored 7 league goals for Atalanta in 2009–10 season.
On 6 July 2010, Valdés joined Portuguese side Sporting CP from relegated Atalanta for a €2,992,500 transfer fee, signing a three-year contract with a €25 million release clause. He debuted for the club on 14 July in a 4–2 loss against Paris Saint-Germain at Parc des Princes, and scored his first goal on 25 July in a 2–1 exhibition match away win over Tottenham Hotspur, where his side's goals were scored by him and his compatriot Matías Fernández for the victory at White Hart Lane. His league debut came on 14 August in a 1–0 away loss against Paços de Ferreira, where was used as left midfielder by his manager Paulo Sérgio, who usually occupied Valdés as central midfielder. On 31 October, Valdés netted a twice in a 2–1 win over União Leiria at Leiria, scoring their first two goals in Portugal and being praised by the press. On 27 November, Valdés scored his side's goal during the derby against Porto in a 1–1 draw, having previously scored a penalty goal the last matchday in a 2–1 win over Académica at Coimbra. Then he continued his streak in the league's first round end on 8 January 2011 in a 2–1 home win over Sporting Braga. However, after two losses, two draws and one victory, his coach Paulo Sérgio was sacked, and with José Couceiro arrival Valdés was relegated to the bench. After an unsuccessful spell with Couceiro, on 6 July 2011, it was reported that Valdés would return to Italy to join Parma on loan with a purchase option worth of €1,8 million in an exchange operation for Valeri Bojinov.
Parma
Parma exercised their option to buy the player in July 2012 after Valdés' well season.