Hooker Dylan Hartley will not be in the Northampton squad when they face Leicester in Friday's semi-final at Franklin's Gardens.
Hartley, who has been sidelined since March with a fractured shoulder suffered against the Tigers, was reportedly in the frame to return to action this weekend.
But with England set to tour New Zealand next month, Hartley has been warned not to rush his return and hopes to be fit for the Saints' Amlin Challenge Cup final against Bath in Cardiff on May 23.
"I was hoping to play this week so my comeback is a matter of days," he told the Guardian.
"There is no point in coming back too early with big games hopefully ahead. We have booked one final and we will know this weekend whether we have another one. Further down the line is the England tour.
"I am progressing day by day. The medics said six to eight weeks when I suffered the injury and we are at six weeks, which is why I always said I was going to try to play this week.
"The decision about when I do play will be clear-cut and it involves the club and England: it is not a case of one side telling me to play and the other not to.
"There is a risk that if I come back too soon I could dislocate the shoulder making my first tackle and I still have to take contact on it."
England are facing a growing crisis at hooker with Leicester's Tom Youngs already ruled out due to personal reasons and Bath's Rob Webber and London Irish's David Paice doubtful due to injury.