In 2003, Valdés defected from Cuba, where he was a member of the Cuban National team. He signed with the Chicago Cubs as a non-drafted free agent in 2004, and was assigned to the Cubsfarm team of the Dominican Summer League. He posted a 7–2 record with a 0.51 earned run average in 16 games for the Dominican Cubs, holding the opponents to a.127 batting average. He also saw action as an outfielder, batting.241 with 12 doubles and 26 runs batted in in 50 games, and was selected for the DSL Post-Season All-Star. Valdés opened 2005 with Double-A West Tenn, but was promoted rapidly to Triple-AIowa on May 9. He went 2–0 in five starts, struck out 18 batters and issued just three walks over 23 innings of work for West Tenn. While in Iowa, he was 6–7 with a save in 25 appearances, working six or more innings in six of his starts, ending 5–0 with a 2.15 ERA in those outings. In 2006, Valdés dropped to 1–3 with a 7.59 ERA in 32 innings for Iowa before being released.
Independent leagues
Valdés joined the independent Can-Am League, going 2–1 with a 5.09 ERA in four games for the Nashua Pride and 7–3 with a 2.81 ERA in 17 games, including 12 starts, for the New Jersey Jackals.
New York Mets
Valdés signed a minor league contract with the New York Mets after the end of the season. He started 2007 with High-A St. Lucie and later was promoted to Double-A Binghamton. He combined for a 0–2 record with a 4.17 ERA and one save in 23 games, before being released. Since 2008, Valdés has pitched winter baseball for the Gigantes del Cibao of the Dominican League and Navegantes del Magallanes of the Venezuelan League. He represented the Dominican team in the 2010 Caribbean Series, in which he led all pitchers in wins and strikeouts and was selected to the All-Star Team. Valdés was invited to spring training with the Mets in 2010. He was sent to the Triple-A Buffalo Bisons to start the season, but was quickly promoted to the major leagues. On May 11, Valdés got his first major league victory in an 8–6 win over the Washington Nationals. On July 6, Valdés was called back as the Mets placed Fernando Tatís on the 15-day disabled list. On August 13, Valdés was optioned to AAA along with Ryota Igarashi to make room for Pat Misch and Francisco Rodríguez. On November 5, Valdés was sent down to Triple-A Buffalo and became a free-agent after refusing the minor league assignment.
St. Louis Cardinals
On November 23, 2010, Valdés signed a minor league contract with an invitation to spring training with the St. Louis Cardinals. Valdés made seven appearances for St. Louis, pitching in 5.1 innings and allowing two earned runs on six hits. He was designated for assignment on August 12, 2011.
On November 10, 2011, Valdés signed a minor league contract with an invitation to spring training with the Philadelphia Phillies. After opening the season with the AAA Lehigh Valley IronPigs, his contract was purchased by the Phillies on May 11, and he joined the club's 25-man active roster.
Houston Astros
Valdés was claimed off waivers by the Houston Astros on October 2, 2013. He was designated for assignment on March 27, 2014. Valdes had his contract purchased by the Astros on April 17, 2014, and was placed on the club's 25-man roster. He was designated for assignment on May 4, and sent outright to the Triple-A Oklahoma City RedHawks on May 6.
Valdés was traded to the Toronto Blue Jays on May 19, 2014, for a player to be named later or cash considerations, and he was assigned to the Triple-A Buffalo Bisons. He elected free agency after the season ended.
Chunichi Dragons
On the December 2, 2014, Valdes signed a $400,000, 1-year deal with the Chunichi Dragons of the NPB. On 26 September, 2017, it was announced that Valdes had been released by the Dragons.
On October 16, 2018, Valdes signed with the Toros de Tijuana of the Mexican League for the 2019 season. On April 30, 2019, during a game against the Saraperos de Saltillo, umpires detected a foreign substance on his left arm, which appeared to be pine tar. He was ejected from the game, and later suspended for 10 games and fined an undisclosed amount for the incident. He was released on November 28, 2019.
