Gennady Golovkin labelled Saul 'Canelo' Alvarez a "clown" after a heated weigh-in on Friday.
After both made weight, Alvarez rushed at Golovkin for the traditional stare down, briefly putting his forehead against the unfazed Kazakh's.
Golovkin (38-0-1) will defend his WBA (Super), WBC and IBO middleweight titles at T-Mobile Arena in a rematch of their drawn fight from a year ago.
The 36-year-old hit out at Alvarez's antics at the weigh-in, promising a "war" on Saturday.
"I saw he is like a clown, he is like a showman, he is not a true guy," Golovkin said.
"Tomorrow, you'll see a real war. This is not a fight, this is not a regular fight, [it's] like a special war."
Alvarez (49-1-2) is fighting for the first time since facing Golovkin a year ago, having served a six-month drugs ban.
The Mexican accepted he got slightly carried away at the weigh-in, saying: "Look, I got excited from seeing all the fans and it motivated me to do that right now.
"I defeated him at the weigh-in, now it's time for me to defeat him on Saturday."