The scrum has become an area of concern for the International Rugby Board following an increase in the number of back and neck injuries being sustained by front row forwards.
O'Sullivan claims the root of the problem can be found in the shift in emphasis from technique to using physical power generated by enormous props to gain the upper hand.
Ireland face feared scrummagers South Africa at Lansdowne Road on Saturday and O'Sullivan is worried by the development of the set piece into such a physically demanding battleground.
"The scrum has been problematic for a while. When you hit the other guy you have to drive his head down into his spine as far as you can and win that collision," he said.
"That has precipitated the teams picking very big props, engaging from as far away as possible and then charging in like the Light Brigade - if you can get away with it.
"The scrum now is basically won and lost on the hit. If you get a big hit on the opposition you won't have much problem winning the scrum.
"It's changed the scrum as we know it. I don't think it's a good thing. There was a time when wily, small, smart props would do very well at the highest level because they could scrummage.
"I don't think it's possible for players like that to thrive any more. The scrum is in transition and has been for a while. The scrum wasn't designed to become a collision but that's what it is now.
O'Sullivan insists Ireland's inability to match rival nations in terms of size means they have been left trailing by the switch in emphasis.
"There's not many Irish front rows out there so this is a problem area for us," he said.
"Historically we were a very good scrummaging nation because even though we didn't always have the biggest props we had the smartest props.
"We had guys who could scrummage at internationals. Now you just have to be big and powerful. We don't genetically produce guys of that physique and that's why we struggle."