Last season's Bundesliga runner-up got back to winning ways against Mainz on Saturday despite another makeshift defensive setup.
The visitors took the lead at the Coface Arena through Pierre-Emerick Aubameyang and, although Maxim Choupo-Moting equalized from the spot, two Robert Lewandowski penalties secured Dortmund's victory.
Klopp had the likes of Mats Hummels, Neven Subotic and Marcel Schmelzer out with injury and was delighted with the character his side showed in front of another makeshift defence.
"We win with a fullback who has not played for six months [Lukasz Piszczek], and with a center back [Manuel Friedrich], who was [out for] almost eight months," he told Dortmund's official website. "I am totally happy with the result and with the development of the game in view of a totally changeable situation.
"This was great fighting spirit."
The win ended Dortmund's two-game losing run in the Bundesliga.
It remains third, seven points behind leader Bayern Munich, which also won on Saturday.