Betis head into the Monday night game at the Estadio Benito Villamarin just four points behind fourth-placed Malaga and still very much in the mix for a Champions League berth, despite not having won in La Liga since January 13.
"We started 2013 with good games, beating Real Zaragoza and Levante, and drawing against Athletic Bilbao," Mel recalled. "It was going well, then we lost two games (against Rayo Vallecano and Atletico Madrid).
"Although I do not like that, I see it as only to be expected for a team that is not made to be at the top of the table."
Betis striker Ruben Castro scored a late winner in the reverse fixture in September, but misses out on Monday as he begins a three-week spell on the sidelines with a right leg injury.
"We hope that does not affect us too much, but clearly it leaves a significant void," Mel said. "Everyone is clear on what they have to do and they will come out well.
"I hope the same thing happens as in the first game.
"We have players who can dominate the ball. I hope we will show Betis' virtues."
Mel, who will also be without midfielders Nosa Igiebor (African Nations Cup duty with Nigeria) and Jose Canas (suspended), added: "We expect to have a great game.
"I have great confidence in the players I have available. I know the team will come out and show their faces. We will try everything to get the victory."
Eleventh-placed Valladolid will be without defender Marc Valiente, whose cheekbone has not recovered from a double fracture suffered when Athletic Bilbao forward Aritz Aduriz elbowed him in the face during the 2-2 draw on February 1.
He joins forward Patrick Ebert (thigh) on Valladolid coach Miroslav Dukic's absentee list.