Manchester City manager Pep Guardiola admits Nicolas Otamendi is unhappy with his limited first-team opportunities this season.
Otamendi has started just eight Premier League games, compared with 33 starts last term, with Vincent Kompany, John Stones and Aymeric Laporte also vying for a place in central defence.
Live Carabao Cup
Guardiola says he understands Otamendi's frustrations and praised the 30-year-old's professionalism this season.
"He's not happy," Guardiola said. "I don't have an answer. When he plays he's happy, when he doesn't play he's not happy.
"But it's not just Otamendi, [it's] everybody. All of them. I don't know what I can do but be honest with myself and with them.
"Of course when he doesn't play he's not happy. In the end with Nico, I know we can count on him at any time in any situation because he's an incredible professional and always he's ready. I'm delighted with him.
"But I can understand him [wanting to play more]. I cannot say anything else."
City face Burton Albion in the second leg of their Carabao Cup semi-final on Wednesday, live on Sky Sports, and Guardiola could look to rotate, with his team already leading 9-0 on aggregate.
Phil Foden is expected to feature at the Pirelli Stadium, while young defenders Philippe Sandler and Eric Garcia have also trained with the first-team in recent days.
However, Guardiola has warned the club's youngsters they will not be gifted a place in his side and must earn their spot on merit.
He said: "I'm pretty sure they are motivated to play in the first team, to play alongside incredible players in competitions and semi-finals. Of course, they are going to be motivated.
"But they have to know how difficult it is to achieve [a place in] the first squad and the first team, not just in Man City but everywhere.
"It is a massive opportunity for them to be close to the first team but it is not easy. We don't give presents because they are nice or something special. It depends on them.
"They have to show us, they have to play their level. Wednesday is a challenge for them but I'm pretty sure they are going to play good because they can do it."