The Baggies have mixed their form in the four matches Mel has overseen, recording two 1-1 draws (with Everton and Liverpool) and losing 4-3 to Aston Villa and 3-1 to Crystal Palace, and the Spaniard now wants a complete performance against the league leaders at The Hawthorns.
"In the first half against Palace we didn't understand the match," Mel said. "It was the same at Aston Villa. We need to focus.
"In the second half (at Palace) we played well, with good mentality. The problem is we only played for 45 minutes.
"If we play for only 40 or 60 minutes then it is impossible to beat Chelsea. So I want to see my players play as one team together, pressing together and dropping off together in set-plays."
He added: "Hard work will help us manage that, although the most important thing for me is we play for 90 minutes.”
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball