Diego Simeone insisted Kieran Trippier is an important player to Atletico Madrid but suggested the right-back may leave the club amid talk of a move to Newcastle.
Eddie Howe's side head into their first transfer window following the Saudi Arabian-backed takeover in October, with Newcastle reportedly submitting a formal bid to make Trippier the first signing of their new era.
The experienced Trippier has repeatedly been linked with a mid-season switch to Newcastle, having impressed during his stint in the Spanish capital, and has also previously been suggested as a target of Manchester United, Arsenal and Everton.
Trippier, who joined the reigning LaLiga champions from Tottenham in July 2019, has managed 67 top-flight appearances for Atletico, while Howe has previously managed the 31-year-old when the pair crossed paths at Burnley in 2012.
Atletico head coach Simeone addressed the transfer speculation on Saturday as he expressed his admiration for Trippier, though he conceded that managers cannot influence players' decisions to leave.
"Kieran Trippier has to decide whether he is leaving or not," Simeone told reporters on New Year's Day at his news conference.
"We will move on following his decision. We have always had these situations where very good players have the possibility of leaving.
"It will depend on what the player wants. We will then look for solutions. We coaches can't do too much in terms of players' decisions. We can only tell Trippier how important he is for the team."
Trippier has hardly excelled for his current team this campaign, failing to register a goal or an assist in 17 games across all competitions, but his previous displays for Tottenham highlight the quality Newcastle would be acquiring.
He created 49 chances in 27 Premier League games in 2018-19, the third-highest for defenders behind only Lucas Digne (71) and Andy Robertson (51), while playing eight and nine games fewer than the respective full-backs.
His addition would offer Howe an attacking outlet and the former Bournemouth manager will also hope the full-back can firm up Newcastle's defense, which conceded 80 league goals in 2021 – the most shipped by any Premier League team in a calendar year.
Howe's side are currently 19th, having won only once in their opening 19 league matches and collected just 11 points.