User blog comment:MarineroLelouch/Power Ranking and Classes./@comment-112.208.53.170-20140212003052/@comment-7418318-20140212092806

I'm still not convinced that Lyon and Gray wouldn't be able to find some way to win a one-on-one now that they know how Racer's magic works. Even without that knowledge Gray was able to make Racer slip on ice and smash into a wall.

And that's all pre-timeskip.

And regarding post-timeskip you should remember Gray's fight against Rufus. He was using ice-make so fast that even Rufus memory couldn't keep up with it. If Gray used that speed with a form that strikes a wide area he might be able to beat Racer without even having to overcome his slowing magic.

Or he could just freeze the floor in a wide area. Racer already showed he's not adapt at moving on ice.

"Racer can easily slit Lyon's throat, he just played around as proven by the manga." Him needing a knife to kill his opponent proofs that he's a powerful mage how?

You say the manga proofed he was playing, but it could just as well be interpreted to proof the exact opposite. That he tried to kill them with only his magic and once it was clear that wouldn't work, he had to fall back to using a knife and a bomb, because he's too weak to kill them with only his magic.