Last week, the prolific Dutchman played his first match since August last year, netting in a 3-0 win over Hamburg in the Bundesliga.
Huntelaar backed up that performance with 90 minutes on Saturday in Schalke's important 2-1 victory over a 10-man Wolfsburg at Veltins-Arena.
The 30-year-old said his second match back was harder than his return and feels he still has plenty of work to do on his fitness.
"I felt very good in our last game against HSV. It was a bit harder for me against Wolfsburg," Huntelaar told the Bundesliga website.
"I played the full 90 minutes and maybe that was why. This game was certainly more demanding for me and I felt it more in my legs.
"I've definitely still got to build myself up more in training."
Huntelaar was critical of his team's display against Wolfsburg, who equalised during the second half despite being down to 10 men.
But he was nonetheless pleased with the victory, which lifted Schalke into fourth in the Bundesliga.
"That's true, even this scrappy win counts in the end. We fought our way out of that weak spell and that's the good thing we can take out of this game," Huntelaar said.
"We didn't let our heads drop after Wolfsburg equalised, so it's not like we didn't deserve our win in the end. This win is also very important for us and for our self-confidence."
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