Speaking ahead of the Premier League trip to Crystal Palace, Ten Hag said: “I hope to avoid that he [Martial] was getting injured [by bringing him off].
“He was complaining, so that’s why he also didn’t train in the week and why he was a question mark.
“He and we both decided that he had to start because his start would be so important in this game [against City] with his pace. Especially with pressing, he is really good and he is a really big element in our pressing, I needed that before half-time.
United are without Jack Butland, who is ineligible, while Donny van de Beek is ruled out for the season, and Jadon Sancho has been on the sidelines.
Diogo Dalot was unavailable for the derby due to injury. Meanwhile, new boy Weghorst could feature.
United face Palace on Wednesday before a crucial clash with Arsenal on Sunday.