Flashscore sources understand that Brobbey was already attracting growing attention after his performances for the Netherlands at the World Cup, with Manchester United among the clubs keen on his progress.
Tottenham Hotspur, Chelsea, Aston Villa, Juventus and Atletico Madrid were also keeping a close watch on his situation, while Bayern Munich had considered him as a potential understudy to Harry Kane.
Despite that growing interest, Sunderland have shown no intention of selling Brobbey and continue to view the 24-year-old as a key part of their long-term plans.
His latest run of form has brought the situation back into focus.
Brobbey has started every Premier League game for Regis Le Bris' side this season, and his three goals against City provided another reminder of the qualities that have attracted attention from bigger clubs.
His hold-up play, physical presence and instinct for scoring goals make him an intriguing prospect at a time when several Premier League heavyweights have struggled for consistency from their forwards.
Man Utd's interest is particularly relevant given their current situation.
As reported by Flashscore this week, United are once again scouring the market for forward options, with particular attention on players they can confidently back to score goals during the second half of the season.
Brobbey fits the profile in some respects, but there is currently no suggestion yet that United are seriously preparing a move for him - and Sunderland are unlikely to make it easy.
Sunderland would value Brobbey at around £50 million and, more importantly, are not operating from a position where they need to sell. His importance to Le Bris' team and the club's wider ambitions mean they are under no pressure to cash in.
There is also an immediate concern for Sunderland, though, after Brobbey suffered an apparent muscle injury while playing for the Netherlands against Germany this week.
He has since been replaced in the Dutch squad by Manchester United forward Joshua Zirkzee and will return to Sunderland for treatment.
The injury means his immediate priority is getting back on the pitch.
But his latest performances have ensured that the bigger picture around Brobbey is receiving renewed attention.