Mel takes charge of the Baggies for only the second time when the local rivals go head-to-head in the Premier League.
"It could be harder for us, preparing to face a team with a new manager," Sky Sports News quotes the Scot as saying.
"His reputation is there for everybody to see, and what he's done in Spain. It's new to him. The league's new to him. West Brom is new to him. We'll see."
The two teams played out a 2-2 draw when they met at The Hawthorns back in November.