England boss Eddie Jones remains confident Dylan Hartley will play a part in the Six Nations after the Saints hooker was left out of the initial squad for the tournament.
Hartley has been nursing a knee injury that has ruled him out of recent matches against Exeter Chiefs, Wasps and Clermont Auvergne.
He will play no part for Saints against Timisoara Saracens on Friday night and will not be fit to face Ireland in the Six Nations opener in Dublin on February 2.
But Jones is optimistic that the influential co-captain will be able to feature for England at some point during the coming weeks.
“Unfortunately, Dylan won’t be available for the Ireland game so we won’t take him to Portugal but we are hopeful he will be back later in the Championship," said Jones, whose side are travelling to Portugal for a training camp next Wednesday.
"Owen (Farrell) will be captain by himself and he will certainly have great support from a number of senior players.”
With Piers Francis also injured - the centre dislocated his shoulder against Exeter on December 28 - Courtney Lawes is the sole Saints representative in the squad.
Jones added: “We are very happy with the squad and have a number of players who have come back from long-term injury.
"We are looking forward to getting across to Portugal and having a good 10-day preparation for the Ireland game.
"“The first thing when we get together as a squad is to get our cohesion back.
"The players have been playing for their clubs with different styles and different playing philosophies, so it’s about getting them thinking about playing the England way.
"The second thing is to get our togetherness stronger to work as hard as we can to make sure we are well connected on and off the field so Portugal is an important camp for us.”
On England’s first opponents in the tournament, Jones said: “Ireland is the best side in the world.
"They are a very well coached and drilled side and have particular things they do well in the game.
"To beat Ireland, we need to compete brutally in all the contest areas of the game.”
A squad of 25 players will depart for Dublin on Thursday, January 31.
England squad for Ireland Test
Jack Clifford (Harlequins)
Dan Cole (Leicester Tigers)
Luke Cowan-Dickie (Exeter Chiefs)
Tom Curry (Sale Sharks)
Ben Earl (Saracens) *
Ellis Genge (Leicester Tigers)
Jamie George (Saracens)
Nathan Hughes (Wasps)
Maro Itoje (Saracens)
George Kruis (Saracens)
Joe Launchbury (Wasps)
Courtney Lawes (Saints)
Ben Moon (Exeter Chiefs)
Brad Shields (Wasps)
Kyle Sinckler (Harlequins)
Jack Singleton (Worcester Warriors) *
Billy Vunipola (Saracens)
Mako Vunipola (Saracens)
Harry Williams (Exeter Chiefs)
Mark Wilson (Newcastle Falcons)
Chris Ashton (Sale Sharks)
Mike Brown (Harlequins)
Joe Cokanasiga (Bath Rugby)
Elliot Daly (Wasps)
Ollie Devoto (Exeter Chiefs)
Owen Farrell (Saracens) captain
George Ford (Leicester Tigers)
Jonny May (Leicester Tigers)
Jack Nowell (Exeter Chiefs)
Dan Robson (Wasps) *
Henry Slade (Exeter Chiefs)
Ben Te’o (Worcester Warriors)
Ollie Thorley (Gloucester Rugby) *
Manu Tuilagi (Leicester Tigers)
Ben Youngs (Leicester Tigers)
Players unavailable due to injury
Piers Francis (Saints)
Dylan Hartley (Saints)
Jonathan Joseph (Bath Rugby)
Chris Robshaw (Harlequins)
Sam Underhill (Bath Rugby)
Anthony Watson (Bath Rugby)