That's according to manager Pep Guardiola, who provided an update on his status after the match:
Manchester City @ManCity
#PEP: It is unfortunate for us and for John and I think he might be out for six weeks with that type of injury. We don't have a lot of central defenders. But the spirit in the team and with all the players is good so we are going to find a solution. #mancity2017-11-18 17:19:40
Stones left the pitch just after the half-hour mark and was replaced by Eliaquim Mangala.
The England international has been one of City's most improved players this season, anchoring the defence. The 23-year-old has been excellent on the ball and with his positioning, freeing up team-mates to be more aggressive in the duels.
As shared by FootballTalentScout, his great form has also carried over to the national team:
John Stones vs Germany 73 passes 97% pass accuracy 2 tackles won 3 interceptions 4 clearances 1 aerial won Brilliant player. One of the best defenders in Europe this season. https://t.co/W1hjRTI3UL2017-11-10 22:21:20
Losing such a player will always hurt, but any prolonged absence will be made worse by City's situation at the centre-back position. Mangala has barely seen the pitch this season and does not seem to have the confidence of Guardiola, while the injury-prone Vincent Kompany has only just returned to the pitch after a lengthy spell on the sidelines.
The Belgian appeared rusty in his first match back and ran into an early booking for a foul on Jamie Vardy on Saturday. Stones covered Kompany, and his effort may have saved his team-mate from an early shower.
Without Stones, City will have to rely on Kompany to return to full form well ahead of schedule and hope the 31-year-old's body holds up in the coming weeks. The Sky Blues' fixture list includes the derby against Manchester United on December 10, as well as a meeting with Tottenham Hotspur on December 16.