Crystal Palace have opened talks with Takehiro Tomiyasu about a permanent deal that would bring the defender back to the Premier League.
The Japan international is training with Palace and was listed among the substitutes for Tuesday’s pre-season friendly against Lens.
Discussions are understood to concern a free-transfer move, with a broad agreement on personal terms in place if head coach Pierre Sage approves the signing.
Sage plans to use three central defenders next season, and Tomiyasu is viewed as a possible option on the left side of that back three.
Tomiyasu has struggled with knee problems in recent seasons. While Palace rate the former Arsenal defender highly, they want to be confident about his fitness.
After leaving Arsenal by mutual consent last season, Tomiyasu joined Ajax and made eight appearances for the Dutch club late in the campaign.
Palace are seeking to reinforce their defence this summer, with first-choice centre-back Maxence Lacroix poised to join Chelsea.
The Eagles have already made at least one bid for Augsburg’s Chrislain Matsima, with negotiations ongoing over a deal worth around €30m (£25.7m).
They also hold interest in a potential loan for Chelsea’s Josh Acheampong, though there is currently no sign Chelsea will allow the 20-year-old to depart.
BBC Sport reported last week that Palace are also strongly interested in Brest centre-back Raphael Le Guen.