Carlos Tevez climbed off the bench for the second half to score just his third Chinese Super League (CSL) goal, days after coach Wu Jingui said the forward was too overweight to play.
But the 33-year-old Argentine, among the best-paid players in the world, could only watch as Shenhua shipped six goals in a nightmare second half at Shanghai Stadium on Saturday.
Shenhua's fifth CSL loss on the bounce left them 12th and Wu, who stepped in after Gus Poyet quit on Monday, said: "We feel sorry for the fans.
"Just like when Manchester City began rising, Manchester United went through a difficult time as well.
"Shenhua are a club with a history and after reflection and some transition, I believe we will come again, just like the current Manchester United team."
There were scuffles in the stands after the match when police moved in on a section of irate Shenhua fans who refused to leave and wanted an apology from the club.
One fan was left unconscious and security personnel forced watching journalists away from the scene.
Derby day in Shanghai was billed as the upstarts of SIPG, for whom Brazilian international Hulk scored twice, against a Shenhua side with deeper roots in Chinese and Shanghainese football.
Shenhua may have the profile and the support, but there was a chasm between the two teams in the second half, with the "Chinese Maradona" Wu Lei also scoring two goals for the home side.
The big win left Andre Villas-Boas's side second in the CSL, but leaders Guangzhou Evergrande are still hot favourites to retain their title.
Evergrande were five points clear with a game in hand to be played later Sunday.
The CSL season ends in early November.
