Bilbao dominated from start to finish against Malaga to strengthen their hold on fourth spot and the accompanying berth in the qualifying stages of next season's UEFA Champions League.
Aritz Aduriz struck early in both halves, while Ander Herrera completed the scoring just after the hour mark when Malaga goalkeeper Willy Caballero let the ball slip through his hands and into the net.
Caballero's effort was symptomatic of Malaga's work-rate in Bilbao and their German head coach was clearly unimpressed after the match.
"The difference has been that we have not done enough to do anything and Athletic has done what it needed and did not have many problems," Schuster said.
"What has been seen is that a team has competed and another has not."
By contrast, Bilbao coach Ernesto Valverde labelled his team's performance 'amazing' and underlined the importance of winning towards the end of the season to 'feed moral'.
Valverde's men maintained a six-point gap over fifth-placed Sevilla with their victory against Malaga ahead of a tough fortnight.
"At this point any win is much more than the three points because you feed moral," the 50-year-old coach said.
"I see very focused players. The effort they are doing is amazing."
Bilbao must travel to Barcelona next week before they host Sevilla in a match that could decide which team finishes fourth and earns the chance to play in the Champions League next season.
Looking ahead to Sunday's trip to the Camp Nou, Valverde admitted Barcelona have more to play for, as they remain in the hunt for the Spanish league title, but he maintained his team have the ability to challenge the Catalan club.
Bilbao defeated Barcelona 1-0 at home at the start of December.
"(The chance to) achieve a title always gives more confidence...but we will still work hard to win or draw with Barca," Valverde said.
