Gennadiy Golovkin called out Saul "Canelo" Alvarez for a trilogy fight after edging a points win over Sergiy Derevyanchenko at Madison Square Garden.
The Kazakhstani scored a unanimous decision to win the vacant IBF middleweight belt in New York City, though he was far from his convincing best and was jeered by fans in the Big Apple.
Derevyanchenko upped his work rate after being felled in the first, but the judges felt GGG had done enough to earn the victory.
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After the fight Golovkin tentatively suggested a rematch with the Ukrainian is an option, but a third bout with Canelo is clearly still the main aim.
"Rematch [with Derevyanchenko]? Absolutely. Big fight for DAZN, for the people, of course I'm ready. I'm a boxer, I'm ready for anything," he said.
"Absolutely I still want Canelo, I'm just open to anybody. There are so many great champions here. Sergiy, a lot of guys. Everything is ready, just call Canelo. If he says yes, let's do it."
The first two bouts with Canelo were classics, with Golovkin contentiously failing to win either fight – the judges scoring the first a draw and the second to the Mexican.
Golovkin's win over Derevyanchenko was just his second fight since losing to Canelo and he conceded his focus was not quite right.
"I want to say thank you so much to my opponent. This was a great job. I respect his team. I told you, he's a very tough guy. This is huge experience for me," Golovkin added.
"Right now, I understand I need more. Focus is boxing. This was a tough fight. I need a little bit more. I need to still get stronger in my camp. Just more serious. I need to work hard. I need a little bit more focus.
"Right now it's a bad day for me, it's a huge day for Sergiy, his team. This is huge experience for me. Right now I know what I need exactly. I lost a little bit of focus."
Thank you to all of my fans who have been there for me and always showed support to #teamGGG . Stronger together pic.twitter.com/WCECSqaSf3
— Gennadiy Golovkin (@GGGBoxing) October 6, 2019
Derevyanchenko sustained a nasty cut in the second round but was able to rally and had Golovkin backing up in a slugfest of a bout.
The 33-year-old is hopeful of earning another shot at Golovkin.
"The cut really changed the fight. I couldn't see at times. And he was targeting the eye. But no excuses, it is what it is, I was trying my best," Derevyanchenko said.
"He hit me in the back of the head. He hit me behind the ear. I didn't really see the punch, but it didn't really affect me that much. I got up and I wasn't really hurt so I continued to fight, so it was nothing, nothing too bad.
"I would like the rematch if it's possible, I'm ready."
Golovkin's promoter Eddie Hearn revealed Golovkin had been battling illness in the buildup to the fight.
"What a fight. It was one of the best fights I've seen. It was brutal," Hearn told IFL TV. "I thought Derevyanchenko was unbelievable.
"He won't say it, but Gennadiy has been ill basically all week, and it was a real struggle for him, and he kept it completely quiet.
"He won't even say anything, but I will, because although Derevyanchenko deserves all the respect in the world, what Gennady had to go through tonight ... the well, when I can't imagine how he was feeling.
"It was incredible, and he showed so much heart. And I thought Derevyanchenko was absolutely brilliant."