Saul Niguez has praised Hector Herrera's attitude but acknowledged he has work to do to earn a starting place at Atletico Madrid.
Herrera has started just one LaLiga match since his arrival from Porto in July, featuring from the outset in the side's goalless draw with Celta Vigo in September.
That game came three days after Herrera scored his first goal for Atleti as a substitute with a timely equaliser in the last minute of 2-2 draw with Juventus in the Champions League.
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Meanwhile, Saul has played every minute of the team's league campaign.