Roy Hodgson could be forced into a late change of plan after Liverpool's Jordan Henderson appeared to suffer an injury on the eve of England's Euro 2016 qualifier against Switzerland.
It is understood Henderson could not complete the full training session at St Jakob-Park on Sunday night and is therefore a doubt for Monday's game in Basle.
Should the Liverpool midfielder be ruled out, Hodgson will be left with just 18 players for the match - two of whom are goalkeepers.
The England manager may choose to move Phil Jones into midfield to replace Henderson or hand Aston Villa's Fabian Delph his first start. Another option open to the 67-year-old would be to deploy James Milner in central midfield.
Hodgson is already without 15 senior players for the match in Switzerland, which is England's first competitive outing since their disappointing World Cup campaign.
Daniel Sturridge was the latest man to withdraw on Friday due to a thigh injury.
The FA refused to comment on the latest fitness concern involving Henderson.
Luis Suarez has made a surprise visit to Melwood on transfer deadline day.
The former Liverpool FC striker posed with his former team-mate Steven Gerrard, with both players holding a Barcelona shirt with the Suarez's name on the back.
Gerrard posted the photo on his Instagram page with the caption:
"He is back bearing gifts. Emotional saying goodbye to the main man this morning.
"Best wishes to a phenomenal player."
New signing Mario Balotelli has told LFC TV that he chose to come to Liverpool because they are 'one of the best teams in England'.
Mario Balotelli has pledged to win "much silverware for the fans" as he confirmed his move to Liverpool FC on his Facebook page.
He said: "I'm proud to announce my return to the Premier League as a Liverpool FC player. Let's make the most out of this amazing challenge ..."
He also uploaded a new banner photo of his face emblazoned on the Liverpool FC motto "you'll never walk alone".
Liverpool manager Brendan Rodgers has called the signing of Mario Balotelli "a smart piece of business."
Speaking to Liverpoolfc.com he said: "There is no doubting Mario's ability; he is a world-class talent and someone who, for such a young age, has vast experience of playing at the very highest level."
He added that he was looking forward to working with the "world class talent" and helping him progress as a player.
He said: "This transfer represents outstanding value for the club and I think we have done a really smart piece of business here."
Mario Balotelli has said he is "very happy" to be moving to Liverpool FC. In a statement on the club's website, he said:
I'm very happy. We've been talking about coming here and now I'm happy to be here.
Liverpool are one of the best teams here in England and the football is very good here.
It's a great team with young players, and that's why I came here.
Mario Balotelli has tweeted about his new club Liverpool FC shortly after the deal for his signature was completed.
YNWA! COME ON LIVERPOOL! ???
Liverpool have announced the signing of Italian striker Mario Balotelli shortly before they kick off against his former club Manchester city.
Steven Gerrard has backed Wayne Rooney to succeed him as England captain.Read the full story ›
Former Liverpool manager Graeme Souness has warned the club against signing Mario Balotelli, describing the move as an "enormous gamble".
AC Milan striker Balotelli is reportedly closing in on a transfer to Liverpool as Reds boss Brendan Rodgers looks to replace the goals of Luis Suarez, who joined Barcelona earlier this summer.
The #16million move for the controversial 24-year-old former Manchester City player is seen as something of a coup by many, but Souness believes it is a risk not worth taking.
Writing in the Sunday Times, he said: "It's an enormous gamble by Rodgers, a gamble I don't think he needs to take because he has a very strong group of players.
"The harmony looks good but he may find, like every previous manager of the Italian, that he will spend more time talking about Balotelli, spending time with him and defending him, than he will the rest of the group put together."
Souness, who managed Liverpool to FA Cup glory in 1992 and has also been in charge of Newcastle, Blackburn, Rangers and Southampton, went on to say that he would not sign Balotelli if he was still in the Anfield hotseat.
He added: "At times Balotelli doesn't seem to enjoy football. Big teams can do without people who pick and choose when they will have a go. It's a high-risk signing. I wouldn't want him."
Balotelli is a proven performer, but the baggage that comes with him is considerable.
His spell with Manchester City from summer 2010 to January 2013 was a whirlwind one, with occasional sparkling performances interspersed with volatility on the field and erratic behaviour off it.
He scored 30 goals in 80 appearances for the club and set up Sergio Aguero's stoppage-time goal against QPR which saw them crowned 2012 Barclays Premier League champions - their first league title since 1968.