Rashford has looked a shadow of his former self in recent weeks, with many wondering whether it is time to take him out of the firing line to allow him to rebuild his confidence.
However, Rangnick says Rashford has been impressive in training and, while he is eager to see the England man improve, it can be tough to judge players when team performances are lacking.
"I was not a striker myself as a player, but as a striker it's all about playing well, scoring goals and getting assists," Rangnick said of Rashford, who has not scored a Premier League goal since August. "And if that does not happen over a period of time it is not so easy
"As long as he's trying to give his very best and he did that in training, there were quite a few training sessions in the last couple of weeks where he trained on a really high level and that's why I always gave him the chance to play again.
"As long as he does that he will always be on my list to play and be in the starting XI.
"Of course it's about showing that on a regular basis and continuously playing on a high level and again for him, as one example, there is still space for improvement.
"The same is true of other young players. We have so many top, talented players and, again, it brings me back to what Cristiano said.
"We have to work and develop as a team together and if it's necessary to speak in a very direct manner to the boys it helps a lot, even in the locker room
"But we can only develop individual players if we develop the performances of the team. This is the only way.
"This is about results, getting good results, which will raise the confidence level and then we can also develop the players individually. It doesn't work the other way around."