Saints star Courtney Lawes looks set to miss England's autumn series opener against South Africa because of a back problem.
Lawes left the squad's Portugal training camp on Friday to return home in order to receive specialist treatment on an injury that initially flared up in Saints' win at Bristol on September 29.
The British and Irish Lions lock was forced off during the second half and then had to pull out of the game against Leicester Tigers on the following weekend during the warm-up.
He was due to return to Vilamoura on Monday evening but given that he will not be able to train fully until Thursday - on the morning the team is announced - his chances of being involved have faded.
"Courtney had a walk through on Wednesday and realised it wasn't right," said England boss Eddie Jones. "Our medical team got on to it straight away.
"He was investigated here, we couldn't get the required treatment here so had to send him back.
"At the moment it seems like it's had the required effect and we'll just wait and see how he comes in tonight (Monday).
"He's had the injury for a while. He missed two games for Northampton. He came back and played a game but it hasn't really rectified itself.
"We're hopeful he'll do some light training on Tuesday. Maybe he'll do some full training on Thursday and we'll make an assessment on whether he's right to go.
"He's a 60-capper, a Lions player, great ball carrier, a good defender. A big loss, so we've just got to pick up the slack."