Spain have eased the 18-year-old back into action after he tore a hamstring in April, limiting him to 141 minutes over the three group games, during which he scored once.
"Lamine Yamal is an excellent player, and he will be for the next 12, 13 or 14 years, maybe even longer," Rangnick told reporters on Wednesday.
"If he stays healthy and keeps a straight head on his shoulders, he can play a lot of matches. He is one of the players we will watch very closely tomorrow, not to give him a lot of room or too many opportunities to start his dribbling actions.
"He is a player that all football fans, no matter where they are from, love to watch. But it is our task tomorrow to let him have the ball as little as possible."
Austria scored six goals in three group-stage matches, one more than Spain, but Rangnick acknowledged his side would need to raise their level against a team unbeaten in 34 matches stretching back to March 2023.
"We all know that we need to do even better tomorrow. Against Spain this is obvious," Rangnick said. "We have to make one further step."
Austria captain David Alaba, who spent five seasons with Real Madrid, said they were fully aware of the quality Spain have at their disposal.
"They play very attractive football. They have enormous quality and individual players that can make a difference," Alaba said. "But we don't want to hide. We really want to play forward and try to be successful."
Austria will be without defender Phillipp Mwene due to injury, but Rangnick said his team had enough options to overcome absences and that he remained convinced they could challenge one of the tournament favourites.
