Espanyol jump up table after win
Espanyol was helped by forward Sergio Garcia and midfielder Victor Sanchez, both scoring and setting up another as Javier Aguirre's side settled into the middle of the league table.
''We got a great result,'' Stuani said. ''We won the game from the start. It was a perfect way to say farewell to the year.''
Garcia opened with a penalty five minutes in after Jesus Rueda felled Stuani in the area.
Garcia then set up Stuani in the 37th after Valladolid had lost the ball in its half.
Sanchez found the net from long range in the 68th and two minutes later crossed for Stuani to tap in his second.
Javi Guerra and Victor Perez salvaged some pride for Valladolid with goals in the 75th and 89th.
Guerra has 11 league goals this season, tied with Real Sociedad's Antoine Griezmann for third highest scorer. Diego Costa leads the league with 19 goals. Cristiano Ronaldo has 17.
Espanyol's David Lopez and Valladolid's Patrick Ebert were both substituted due to apparent muscle injuries.
The league takes a two-week winter break from Monday.