The Paraguayan striker, who joined Frankfurt from Abu Dhabi outfit al-Jazira Club in July, ruptured the anterior cruciate ligament in his right knee at the Volkswagen Arena and is expected to be out for the rest of the calendar year.
"Nelson is a fighter," said Frankfurt coach Thomas Schaaf following the 2-2 draw. "We will do everything we can to get him fit again as quickly as possible. It goes without saying that he has the full support of everyone here at Eintracht."
Before joining Frankurt in the summer, Valdez had previously scored 40 goals in 220 Bundesliga appearance for both SV Werder Bremen and Borussia Dortmund. He has also made 66 appearances for Paraguay since making his debut ten years ago, scoring 12 goals.