Sergio's side are currently bottom of the table with just three points to show from their eight matches thus far, while Athletic are 11th in the division with nine points from their opening seven games.
There is no getting away from the fact that it has been a disappointing start to the season for Valladolid, who have picked up just three points from their opening eight matches to sit rock bottom of the division.
The White and Violets are one of just two La Liga teams - the other being Huesca - yet to win a match this season, which will concern their supporters, even at this relatively early stage of the campaign.
Sergio's side are the joint-lowest scorers in Spain's top flight with just five goals, while they will enter this weekend's contest off the back of a 2-0 defeat at Villarreal.
Valladolid have actually only picked up one point from their last five league matches, and the early indications are that they could be in for a tough battle to retain their top-flight status this term.
Athletic, meanwhile, will enter Sunday's clash in good form, having won two of their last three in the league, including an impressive 2-1 home success over Sevilla last weekend.
Six points from the last nine available has helped Athletic move into 11th position in the table, but they have still lost four of their seven matches in Spain's top flight during an inconsistent start.
Gaizka Garitano's side finished 11th in La Liga last term, and it is difficult to imagine them pushing towards the European spots in 2020-21 considering that they were unable to improve their squad over the summer.
Athletic will be eyeing another three points on Sunday, though, and the Basque side recorded a 4-1 victory when they last locked horns with Valladolid back in March.
Real Valladolid La Liga form: DLLDLL
Athletic Bilbao La Liga form: WLLWLW
Nacho Martinez is back after serving a suspension against Villarreal, though, and the Spaniard is expected to return to the back four for this weekend's contest.
Head coach Sergio is likely to shuffle his pack for Sunday's clash, with Sergi Guardiola and Jawad El Yamiq both in line for starting spots, but Shon Weissman should keep his spot in the final third of the field.
Real Valladolid possible starting lineup:
Masip; Perez, Fernandez, Yamiq, Nacho; Orellana, Alcaraz, Emeterio, Villa; Weissman, Guardiola
Athletic Bilbao possible starting lineup:
Simon; Capa, Alvarez, Martinez, Yuri; D Garcia, Lopez; Berenguer, R Garcia, Muniain; Williams
We say: Real Valladolid 1-2 Athletic Bilbao
Valladolid's form this season has been extremely disappointing, but Athletic appear to have turned a corner since the October international break. Garitano will be desperate for his side to pick up another three points ahead of the next two-week break, and we fancy the visitors to triumph on Sunday evening.