Saints will still be without a huge number of their first-team squad for Friday's crucial Gallagher Premiership game at Newcastle Falcons (kick-off 7.45pm).
Boss Chris Boyd provided an injury update on Wednesday, but there was little good news on possible returnees.
Luther Burrell, who suffered concussion in the defeat to Gloucester at Franklin's Gardens on April 7, looks likely to be the only recent absentee who is able to make a comeback this week.
It was hoped that Dylan Hartley would recover in time to play at Kingston Park but though he has 'trained really well', the England hooker will not feature against Newcastle.
Hartley has not played since starting in Saints' December 21 win at Worcester Warriors and he had surgery on a 'grumbly' knee injury back in February.
"He trained really well this morning but time's running out for Dylan this year," said Boyd.
"He's obviously not going to play against Newcastle.
"We've then got two games left in the regular season, against Worcester and Exeter with a European finals weekend off in between.
"The long-term hope if we wind the clock back to post-operation was that he would make one of the last three games at some point in time.
"If he made Newcastle he could have got three games under his belt, if he made Worcester he'd get two or Exeter he'd get one.
"We're still optimistic that Dylan will be in a position to be selected at some stage between now and the end of the season."
Flanker James Haskell also remains unavailable.
"He's still battling post-operation around his ankle and his foot," Boyd said.
"He's got some long-term stuff going on around that foot so it's been really frustrating for him.
"He's worked really hard but he hasn't been able to get the old body where it needs to be and he's not ready for selection."
But good news for Saints comes in the form of Burrell and fly-half Dan Biggar, who was unable to kick late on at Harlequins a couple of weeks ago.
"Dan's got a little heel niggle, but he's fine, he's trained well all week and he'll be there on Friday night," Boyd said.
"Luther is available for selection but Heinrich (Brüssow, who has also been battling concussion) is not.
"Luther is back in the fold if we need him."
Piers Francis will not be fit to feature after he was forced off at Harlequins with a knee problem, meaning Saints could call on Burrell to line up alongside Rory Hutchinson at centre.
"(Alex) Moon, Francis, (Lewis) Ludlam, (James) Fish were the short-termers and I don't think any of those are going to make this week," Boyd said.
"We've certainly stretched our resources pretty hard and we're just hanging in there.
"The nice thing is that when people have been asked to step up, by and large they've done a good job for us.
"We've had some disappointment around people who've had long-term and short-term injuries but invariably when someone's been given an opportunity to do a job for us they've been pretty good.
"It's been a pretty positive part of the injury situation."
Saints' current injury list...
Andy Symons (knee)
Harry Mallinder (knee)
Mike Haywood (knee)
Dylan Hartley (knee)
Ehren Painter (calf)
Paddy Ryan (knee)
James Haskell (toe)
Fraser Dingwall (ankle)
David Ribbans (ankle)
James Fish (concussion)
James Craig (hamstring)
Nafi Tuitavake (elbow)
Ollie Sleightholme (ankle)
Heinrich Brüssow (concussion)
Lewis Ludlam (shoulder)
Alex Moon (ankle)