Southampton defender Florin Gardos faces up to seven months on the sidelines with a knee injury, meaning Ronald Koeman is targeting to at least one new centre-back.
Signed from Steaua Bucharest last summer, the 26-year-old had looked set to get a chance to prove his worth at St Mary's following Toby Alderweireld's exit.
However, Romania international Gardos now faces "six or seven months" out with a knee injury - a huge blow to player and club.
"Very sad news," manager Koeman said after Saints' 3-0 win at his former club Feyenoord.
"He was going into his second season in Southampton and young, and that type of injury and you lose six or seven months and everybody is disappointed."
Gardos' injury, coupled with Alderweireld's decision to join Tottenham rather than convert his loan from Atletico Madrid into a permanent move, has heightened Koeman's need to strengthen his options at centre-back.
"That's the priority, to bring in one or maximum two centre-backs," the Dutchman said. "It's too small with Maya (Yoshida) and Jose (Fonte).
"Ok, we have (Jack) Stephens, we have (Jordan) Turnbull, but they are young and still they have to improve themselves and that's the point for attention at the moment, the centre-back position."