Mark Coleman is only a little smaller, and Fedor submitted him like he was a ten year old school girl (and afterwards, he cried like one).
He is quite a bit smaller actually. Lesnar cuts down from 280 pounds, Coleman is about 220-230 pounds like Fedor I believe (someone correct me if Im wrong), so the strenght difference wasn't as obvious as it would be with Lesnar, who is also by far more agile than Coleman. Either way Coleman got subbed by Fedor twice, which is why I said Lesnar would need couple years of sub defense training too so he wont get armbarred after tossing first hammerfirst down at Fedor.
Um... Fedor fought Tim Sylvia, struck with him, and knocked him out (even though he finished with the submission).
Sylvia is way too slow in my opinion, I bet Liddell, Silva (actually both Wandy and Spider) and Shogun would finish him about as efficiently as Fedor did. I found whole Fedor-Sylvia fight to be a waste of time to begin with really.
Either way I mentioned it would have to be a quick counter puncher like Liddell.
Comparing Liddell with Sylvia makes no sense at all really because their styles are way difference, and Sylvia's slow movement combined with bad TDD and sub defense leaves way too many holes in his game against guys like Fedor, Nog, Randy and even Mir like we saw.
Also, with Fedor it's not a matter of shot-defense. It has to be someone who's got a world class clinch game, and there's nobody with that level of clinch game that can stand with Fedor.
Wandy comes into my mind first. Infact Wandy-Fedor in a ring could be very entertaining fight to see if Wandy decided to move to HW for some reason and packed a 20 or so extra pounds of muscles.
Anyway Im just tossing possible ideas & names here. I don't think there is fighter Fedor wouldn't be the favourite against right now, but the guys I listed would in my opinion have pretty good chances to do it.
Also Fedor himself seems to be interested about fighting Lesnar in the future:
“I like Brock Lesnar very much. I haven’t seen too much of his fights, but I enjoyed seeing what I saw. I see him very strong physically and someone who has a lot of potential and a very bright future in the sport. It’s definitely a fight that would be interesting to me and a fight I would like to have and he would defiantly be a very worthy opponent.”