Striker Nick Woltemade scored his first international goal to secure a 1-0 win over Northern Ireland in Belfast on Monday, and put Germany top of Group A ahead of the next set of matches in November.
The four-times World Cup winners are on nine points in Group A, ahead of Slovakia, who beat Luxembourg 2-0, on goal difference. Northern Ireland are third on six. The group winners qualify automatically for the finals and the runners-up advance to the playoffs.
"Obviously, we already have the squad ahead of the World Cup in our heads," Nagelsmann said. "But the first thing is the qualification.
"We have to see the development within the teams they play for. Fifteen or 16 players have now been together for about two years. So a certain squad structure is identifiable," he said.
The Germans have been for months without injured playmaker Jamal Musiala, first-choice keeper Marc-Andre ter Stegen and forward Kai Havertz.
Nagelsmann, however, is satisfied with his team's progress, despite the injury absences that also include Antonio Rudiger, Niclas Fullkrug and Benjamin Henrichs.
"We have done more than in the weeks before. We have talked with the players. We have taken steps forward as a team," he said.
Germany are away to Luxembourg on November 14 before hosting Slovakia three days later.