The 18-year-old is close to returning to action for Chelsea after suffering an Achilles injury in April.
Speaking to Goal, Melchiot said: "A good Hudson-Odoi would give me the most problems as a defender.
"If he can get back to where he was before I think he would be the most dangerous prospect Chelsea has.
"I like Hudson-Odoi. I was sad when he was injured as it was at a crucial moment. The balance of the team was perfect. Hazard was on the left-hand side pulling a lot of attention. Then when Hudson-Odoi got the ball, he had a one-on-one.
"Pulisic will have to first earn the attention of markers like Hazard did. If Hudson-Odoi is back in the team, then he might eventually find himself doubled upon. He has to think smart and deal with it. People didn't know him before so he could get away with it."