The former Villarreal striker struck twice on debut in the friendly win against Kitchee in Hong Kong this week.
Witsel said, "Good for him and for us, he is a profile that we are going to need. He is going to be important for us and it is good for him that he scores a goal in the first game. It was a game to put more minutes in his legs. The conditions of heat and humidity is not easy.
"We played well. The most important thing is to get minutes in our legs to be ready to start the season. Now we have one game left against Juventus and it will be the same."
Witsel continued: "So far we have a very good group, let's see what will happen in the next few days. Those of us who are here still don't know much. We have a very good squad and we want to have a great season.
"Now the most important thing is to be physically well, to be all together in Madrid for the next game against Juventus. And match by match as always. We want to start strong. Our objective is also to change the away games and maintain strength at home."