Bobb, who joined Man City from Valerenga in 2019, put in a number of impressive performances during Man City's pre-season tour of the USA, before going on to produce another fine display in Saturday's Community Shield against Manchester United.
The youngster provided the assist for Bernardo Silva's 89th-minute equaliser at Wembley, before his teammates held their nerve in the subsequent penalty shootout.
After playing the majority of the Community Shield success, Bobb was seemingly in contention to start Sunday's opening league game against Chelsea at Stamford Bridge.
Bobb suffers major injury blow
However, the 21-year-old now looks set for an extended spell on the sidelines after suffering a leg injury in training.
According to The Times, the Norway international fractured a bone in his leg in a non-contact situation when he turned in Wednesday's training session.
The Citizens will have to make a full assessment before an exact timeframe can be given for Bobb's rehabilitation process.
Man City will also decide whether to send Bobb to Barcelona to be examined by renowned specialist Dr Ramon Cugat.
Could Man City be forced into the transfer market?
The Premier League champions recently allowed Julian Alvarez to complete £82m transfer to Spanish side Atletico Madrid.
Pep Guardiola was reportedly willing to sanction Alvarez's departure because he felt that Bobb would have a bigger role to play in the 2024-25 season.
The Man City manager praised Bobb and James McAtee following the Community Shield, claiming that the club "could rely on them" for the new campaign.
With Bobb now out for an extended period, Guardiola must decide whether he feels he needs to sign another attacking option before the transfer window shuts on August 30.
In addition to Bobb's absence, Man City must assess Jack Grealish ahead of Sunday's clash with Chelsea after the 28-year-old missed the Community Shield with a small injury.