Valdez left Werder Bremen in August 2006 to join fellow Bundesliga side Borussia Dortmund for a fee of €4.7 million on a four-year contract, where he was given the number 9 shirt. Within that four years, he scored 16 goals in 113 Bundesliga appearances and helped Dortmund qualify for the 2010–11 UEFA Europa League. After an impressive performance at the 2010 FIFA World Cup with Paraguay, Valdez joined La Liga side Hércules for €3.5 million on a three-year contract, where he partnered with French striker David Trezeguet. He became the most expensive signing in the club's history and scored a double on his debut in a 2–0 win at the Camp Nou against Barcelona on 11 September. After eight goals in 25 league appearances in the 2010–11 La Liga season, Hércules were relegated to the Segunda División and Valdez was then transferred to Russian Premier League side Rubin Kazan for €4 million. Valdez was later loaned out to Valencia and went on to enjoy stints with Al Jazira and Olympiacos. In July 2014, Valdez returned to the Bundesliga and signed with Eintracht Frankfurt, being reunited with former Werder Bremen coach Thomas Schaaf. Valdez played from 2015 to 2016 with American club Seattle Sounders FC in Major League Soccer, scoring in the playoffs and winning the MLS Cup in his final season.