Southampton head coach Ralph Hasenhuttl has admitted right-back Tino Livramento may require surgery on his injured knee.
The 19-year-old has starred at St. Mary's this season since his £5m from Chelsea in the summer, but he has not featured for the Saints since the Boxing Day victory at West Ham.
Back-up option Yan Valery filled in in the FA Cup third round victory over Championship side Swansea, but after he was sent off for two bookable offences captain James Ward-Prowse was forced to fill in at right-back.
Speaking in his post-match press conference, Hasenhuttl revealed he was worried about the extent of Livramento's injury.
"The meniscus injury, even if it is a light one... I know this from my own son, it was a year out," he said.
"We don't know. At the moment we try it without surgery, but we have to look how serious it is. It is always an alarm for me when they (medical team) don't want to speak.
"It is not good when they are not coming to me. But I will go to them every day to ask them."
Speaking about the possibility of Ward-Prowse covering at right-back again in the meeting with Brentford on Tuesday night, Hasenhuttl said: "I will ask my captain what he says."
The match at Swansea was played behind closed doors per the Welsh government's current regulations. Saints' Austrian coach added: "It was a strange situation because we are not used to it anymore.
"But I know that we can fight. I know we have a team with passion and high workload, but the fixtures this week now are coming very quick.
"It does not get any easier with Brentford on Tuesday."