Zenit St Petersburg's record signing Hulk has threatened to quit the Russian club following a heated exchange with coach Luciano Spalletti during Tuesday's Champions League win at AC Milan.
The Brazil striker reacted angrily after the coach substituted him late in the game at the San Siro, which Zenit won 1-0.
Spalletti was seen extending his hand, trying to greet Hulk as he was leaving the pitch but the Brazilian just walked by without looking at the coach before having a heated discussion with the Zenit staff near the sideline.
"If the situation with the coach does not resolve itself I may leave the club in the January transfer window," Hulk, 26, was quoted as saying by local media.
Spalletti, however, played down the incident.
"All big players don't react well when they're substituted," the Italian told the club's website.
"The most important thing is that we won the game."
The Russian champions beat Milan thanks to a first half strike by captain Danny in their final Group C match to finish third and qualify for the Europa League.
Hulk has had a tough time settling in St Petersburg, with several senior Zenit players apparently unhappy after the club splashed out a Russian league record 60 million euros just before the transfer deadline to sign the striker.
Zenit demoted Russia skipper Igor Denisov to the reserve team in September after he refused to play, issuing an ultimatum to renegotiate his contract in line with what Hulk was making.
Denisov was later allowed to rejoin the first team after making an apology.