Let's say you could put a modern fighter in a time machine and have him fight Igor in one of those crazy underground old school vale tudo tournaments. While MMA has obviously improved in terms of technique since the 90s, I still think that in a "real fight" the no rules format would likely give Igor a decent chance against many of the top guys in the UFC around his weight. He was really crafty with some of the moves that weren't even allowed under Pride rules like headbutts. And he had bare knuckle fighting experience. Remember that there would be no camp for a specific opponents, no gameplan, absolutely no rules, it would be a bare knuckle fight with no rounds. Basically just lock the cage and let them bang, like in a real streetfight. I think Igor beats Bisping and shatters Rockhold's pathetic chin. Maybe loses to elite wrestlers like DC and Romero if they take him down and headbutt him and knee him. Vs Rumble it would be a kill or be killed kind of fight.