London - George Kruis has added to England's injury woes after being ruled out of the Grand Slam champions' Six Nations opener against France at Twickenham on Saturday with a knee ligament injury.
The Rugby Football Union said Saracens lock Kruis, a key member of the side that won the Grand Slam in 2016, would see a specialist on Thursday.
"We'll have to wait and see what the specialist's prognosis is, but we're not ruling him out of the Six Nations at this stage," said England coach Eddie Jones of the 20-times capped Kruis.
It now appears as if Courtney Lawes and Joe Launchbury will reform the second row partnership that started against South Africa and Fiji in November when Jones announces his team to play France on Thursday.
Meanwhile Maro Itoje, Kruis's lock partner for both club and country, is set to make his first Test start at blindside flanker after ex-England captain Chris Robshaw was previously ruled out of the entire championship following shoulder surgery.
The 22-year-old Itoje himself missed England's end-of-year campaign in November with a hand injury.
Kruis could well be ruled out of England's second match of the tournament, against Wales in Cardiff on February 11, as well but after that match there is a break in the tournament, with the champions not in action again until they face Italy at Twickenham on February 26.
The absence of Kruis adds to an already extensive list of injuries confronting Jones.
Bath wing Anthony Watson is currently sidelined with a hamstring injury, while James Haskell is struggling to overcome the lingering effects of a foot problem and fellow back row Billy Vunipola will miss at least the opening rounds because of knee damage.
Prop forward Mako Vunipola, Billy's brother, is also sidelined but front row rival Joe Marler has made a quicker than forecast return from a fracture to his lower left leg.
Injury-prone England centre Manu Tuilagi will play no part owing to a season-ending groin injury.
But England defence coach Paul Gustard, speaking earlier Wednesday, said the squad had the strength in depth to replace Kruis and any other injured players.
"We pride ourselves in the quality we have around the country," said Gustard.
"We're proving we can cope with people not being in the team and while there are people missing in this Six Nations there are also people returning and that's also exciting."
England are on a 14-match winning streak, with 13 of those victories coming since Australian coach Jones took charge following the team's first-round exit on home soil at the 2015 World Cup.
But Gustard insisted that record would count for little if England did not beat France on Saturday.
"All we want to do is go out and win," he said. "Our entire focus since January 1, even before that since we beat Australia at Twickenham, is to beat France.
He added: "France are a very good team. We saw progress from them in the autumn and they ran a couple of teams close.
"Traditionally they have got a very strong pack. They've got a big heavy tight five and backs who can play with verve and when the ball comes loose and alive they find another gear. From that, we have to respect them."