Valencia coach Nuno Espirito Santo felt an injury to striker Rodrigo was a pivotal moment in his team's 2-1 loss to Atletico Madrid.
The La Liga encounter at Estadio Vicente Calderon was goalless in the first half when Rodrigo pulled up during a Valencia attack and left the field on a stretcher.
Errors from the visiting centre-backs Shkodran Mustafi and Aderlan Santos gifted the opening goal to Jackson Martinez and Atleti's Belgium international midfielder Yannick Ferreira Carrasco added a superb second before the break.
Rodrigo's replacement Paco Alcacer reduced the arrears from the penalty spot with 18 minutes remaining but Los Che were unable to force an equaliser.
"There were two important moments," Nuno said. "Rodrigo's injury disrupts our plans and the first goal, it's a mistake, obviously.
"We have tried to balance and push higher in the second half.
"In the first part we could not control the game, we could not create. In the second half we improved and we were close to what we want.
"We had a chance to equalise. We must rectify and work harder to be what we want."
"We are not proud but we are convinced that we must continue working in this way."
Nuno refused to be drawn on whether Rodrigo's expected absence would result in Alvaro Negredo being brought in from the cold – the former Sevilla and Manchester City forward having once again missed out on a place in the matchday squad, as he did for Tuesday's Champions League encounter against Gent.
"This week we prepared the game with a plan, with players we thought were best," Nuno added.
"For next the game we'll use our best options too."
Valencia are in action next Saturday at home to local rivals Levante, who sacked coach Lucas Alcaraz following a 4-0 loss to Real Sociedad on Sunday.
