Chris Boyd says Saints are still searching for the right time to bring Heinrich Brüssow back into the team after the South African was forced to withdraw from Sunday's game at Wasps.
Brüssow was named in the starting 15, lining up in the No.7 shirt, but he 'just didn't feel quite right', meaning Paddy Ryan was brought in for his Saints debut.
Taqele Naiyaravoro took Ryan's place on the bench and went on to score a crucial try as Saints secured a 15-14 Premiership Rugby Cup win, recovering from 14-0 down.
Saints' next game in the competition comes at Gloucester on Friday night, but Brüssow, who has not played since September 15 due to concussion, remains a doubt.
"Heinz is there or thereabouts but we're just trying to find the right time to drop him back in," Boyd said.
"He's been coming on nicely but he just didn't feel quite right.
"He might be back on Friday, he might not.
"But in his absence, Lewis Ludlam has been particularly good for us in that space and we've got Teimana Harrison to come back who has been one of our best players all year.
"We've also got Tom Wood to come back in, who played well against Bristol, so we've got good cover in the loose forwards."