The promoted team, who until now have used a rental stadium to hold its support drawn from a village of 3,300 people, lead the standings after 17 matches on goal difference from champions Bayern Munich.
"We are deserved "winter champions"," multi-millionaire software pioneer Dietmar Hopp, who has bankrolled the club since the 1990s, told German paper Bild on Tuesday.
"If we keep it up... we are a force to be reckoned with. I am not saying we will be champions but we will hang on up there," said Hopp, who will watch his team's second half of the season from a newly-built 30,000 seat stadium.
"I would not have believed it if someone would have told me that after 17 matches we would have had 35 points," Rangnick said.
"We cannot take big steps anymore. Now it is all about maintaining that level and improving step by step."
Hoffenheim's achievements this season are even more remarkable given Bayern's resurgence in form.
After a rocky start under new coach Juergen Klinsmann, the champions have improved since France midfielder Franck Ribery's return from injury in late September, winning eight out of the last ten league matches.
Klinsmann's side have also qualified for the knockout stages of the Champions League and the last 16 of the German Cup with ease.
Bayern have felt uncomfortable at the domestic spotlight falling on Hoffenheim with manager Uli Hoeness saying their success was purely down to Hopp's money.
"We never looked for a star," Hopp said. "The fact that a star has found his way to us on favourable terms does not mean our strategy changes."
