There's a problem here, and it's the same problem Sam had pointed out time and time again with Dean - Sylar is not a demon. He knows what that feels like, how to differentiate between the demon and the true person inside the body, knows how to pull one with minor damage to the other. But Sylar doesn't feel like a demon exactly, doesn't feel like he belongs entirely either, which means Sam has to concentrate even harder, focus-

Which is interrupted a bit when he's punched in the shoulder.

His concentration wavers while he reacts, letting out a shout of pain and then lifting his arm again. He's pulling again but there were several seconds where Sylar would have been perfectly able to pull himself together a bit.