But Overeem says that won't be the case by the end of the year.
"Cain Velasquez is No. 1 now because I haven't competed against the names," Overeem told MMAFighting.com. "So there is that argument, that I haven't fought the caliber opponents I should -- I wanted to, but either they wouldn't fight me, or the schedule didn't work out. But that's what this tournament is about."
But Overeem said he's very confident that he'll beat Fabricio Werdum in his first fight in Strikeforce's upcoming heavyweight tournament, then he'll beat either Fedor Emelianenko or Antonio Silva in the second round of that tournament, and then he'll win the tournament final. Overeem thinks the whole tournament will progress quickly enough that he could fight three times before Velasquez returns from shoulder surgery, and that by then MMA fans will recognize Overeem as the top heavyweight in the sport.
Overeem's April fight with Werdum will be a rematch of a 2006 Pride bout that Werdum won by submission. But Overeem said he's a far better fighter now than he was then.
"I'm very motivated, very healthy, very confident," Overeem said. "Everything is different now for me than when I fought Werdum. I was a light heavyweight then and I'm a heavyweight now. I'm much better than I was then."
Overeem said he's so confident in his ability to keep the fight standing against the dangerous Brazilian jiu jitsu black belt that "It might as well be a K-1 kickboxing match of three five-minute rounds."
The heavyweight tournament gets started on February 12, and Overeem will be paying particularly close attention to that night's fight between Emelianenko and Silva. When asked to play oddsmaker for that bout, Overeem said, "60-40 Fedor."
"Silva is a big guy who could give Fedor trouble," Overeem said. "I just want to watch and see what happens. I'm really not concerned about that, I've just got to beat Werdum and I'll fight the winner."
And if Overeem beats Werdum and then beats the Emelianenko-Silva winner, he thinks he'll be more than just the Strikeforce champion. He'll be the top heavyweight in the world.