Forum:Gravekeeper's Watcher VS Morphing Jar in Damage Step

After all, Can I negate the effect of Morphing Jar in the damage step with the Gravekeeper's Watcher? In his rulings says I can't, but he is a quick effect monster and I see no reason to not negate with him. I think Yu-Gi-Oh! Wikia is contradicting himself, because the rules of quick effect monsters says I can use the effect in the damage step.

Someone can help me?