Atletico Madrid winger Thomas Lemar has not lived up to expectations at the club, according to head coach Diego Simeone.
The 24-year-old, who joined in a €70 million (£60m/$78m) deal from Monaco in July 2018, has struggled for consistent form in La Liga.
The France international has been heavily linked with a possible move to Arsenal this month, although a hamstring injury could complicate any potential mid-season transfer.
Speaking ahead of Saturday's league meeting with Levante, Simeone did not state whether Lemar could be allowed to leave in the January window but did admit the player's performances have been something of a disappointment.
"Facts speak better than words. Lemar is an important player who hasn't been able to develop his game but who has characteristics that others don't have," Simeone told a news conference. "Let's hope he has a good moment when he comes back from injury.
"Now, if Lemar can stay or not... we know that agents work in an exemplary way. Clubs work in terms of the needs of the clubs. But, as a footballer, every time he has been available, he's played a lot more than he hasn't played.
"His characteristics have always excited me. But he hasn't been able to live up to expectations."
Atleti have been linked with moves for strikers such as Paris Saint-Germain's Edinson Cavani and Borussia Dortmund's Paco Alcacer, having found it difficult to score enough goals this season.
Simeone is open to transfers but is not prepared to discuss players who do not play for Atleti.
"Like every year, there is the possibility of players leaving or arriving in January," he said. "We've spoken to the club about this, about the situation that we have and when [the chances of signing players] happen, if they happen, we'll find out.
"What concerns me is what happens against Levante. Aside from the game we're playing, the club knows what we've been talking about and will work to bring the best to the club and the team."
When pressed on interest in Cavani, he added: "I don't talk about players who aren't in our squad."
Atleti are fourth in La Liga after 18 games, seven points behind leaders Barcelona.