Shanghai Shenhua cross the city into enemy territory on Saturday to face Shanghai SIPG for Chinas biggest derby, an intense rivalry spiced by money and identity.
Shenhua make the trip in turmoil: former Chelsea and Tottenham Hotspur midfielder Gus Poyet quit as manager on Monday under pressure with the club languishing below mid-table in the 16-team Chinese Super League (CSL).
Shenhua shelled out some of the highest wages in football -- reported weekly wages of 730,000 euros -- to lure forward Carlos Tevez to China this season but he has scored just twice and is not expected to feature at the weekend after Poyet's replacement Wu Jingui said the Argentine was overweight.
In contrast, Andre Villas-Boas on Tuesday guided SIPG into the semi-finals of the Asian Champions League for the first time and they sit second in the CSL.
They acquired Oscar from Chelsea for an Asian-record 60 million euros ($72 million, £54 million) in the winter and also boast his fellow Brazilian international Hulk up front.
But to Shenhua fans, SIPG are unwelcome upstarts who bought their way to newfound success and are supported by turncoat former Shenhua followers or out-of-towners who do not understand the city of 24 million, its local dialect or its football.
It's a bit like how Manchester City fans accuse United supporters of being from just about anywhere in the world except Manchester.
Shenhua fans sometimes chant in Shanghainese, burnishing their claim to be the true home side.
Wang Wei used to be a Shenhua fan. Now he supports SIPG.
Changing sides like that would be virtually unheard of in established football fan cultures such as Britain's, but Wang is not alone.
"Lots of SIPG fans used to be Shenhua supporters, it is just that Shenhua are too disappointing these days," said the 29-year-old.
"Shenhua always thought they were the big brother in Shanghai but now there is this little brother coming out with better performances and deeper pockets."
The two clubs may dislike each other from the fans up to the boardroom, but unlike decades-old football rivalries elsewhere, Shenhua-SIPG really only goes back to 2013.
Shenhua became a fully professional club in 1993, but its roots go back decades, whereas SIPG only came into being in 2005 under the name Shanghai East Asia.
In 2013 the latter gained promotion to the top tier and was rebranded Shanghai SIPG after the wealthy Shanghai International Port Group stepped in. That's when relations quickly soured.
Steve Crooks, a Shenhua fan since 2010, uses the same sibling analogy.
"There was this big-brother, little-brother thing when SIPG were coming through the leagues because they started as a youth academy and they had a lot of Shanghainese players and they played nice, passing football," said Crooks, who writes for the Wild East Football website dedicated to the game in China.
- Toxic atmosphere-
"There was a very non-threatening rivalry, then they got this big corporate takeover and changed the name, so it became very much old money versus new money."
Crooks said the fact that some abandoned the blue of deteriorating Shenhua for SIPG red makes for a "toxic" atmosphere come derby day.
"It used to be a lot friendlier but in recent years, since the takeover, there is a lot more needle and it's nastier and you see occasional scuffles outside the ground," he said.
Results in the derby have been roughly split between the two sides in recent years, but Shenhua are seeking revenge on Saturday for a 3-1 home defeat in May.
Andy Strong, another Shanghai expat and an SIPG supporter, says accusations that they bought their way to success are hypocritical, pointing to Tevez's wages.
"A lot of it stems from bitterness and jealousy," said Strong, adding that several players in Villas-Boas's starting XI came through SIPG's youth ranks, including 25-year-old Wu Lei, the so-called "Chinese Maradona".
Despite the rivalry, Strong, sports client manager at the Shanghai-based sports marketing and investment company Mailman, said he hoped Shenhua -- in disarray after going through a succession of coaches -- will rise once more.
"I would much rather have a strong Shenhua side and have a competitive derby, fighting each other for the league title and AFC Champions League."