Rio Ferdinand is doubtful for England's World Cup qualifier against Andorra this weekend after missing training on Wednesday.
The Reds defender, who has 69 caps for his country, sat out the session at London Colney because of a stiff back, a problem which also affected him on United's pre-season tour of South Africa in July.
England are hopeful Ferdinand will shake off the injury in time for the game in Barcelona's Olympic Stadium on Saturday, but if he fails to recover his place could be filled by Reds team-mate Wes Brown.
Brown trained on Wednesday after previously resting his knee as a precaution and could slot into Ferdinand's centre-back role against the European part-timers, alongside Chelsea captain John Terry.
England are already missing Owen Hargreaves (knee) and Michael Carrick (ankle), but Wayne Rooney is expected to start up front alongside Jermain Defoe.
Rooney has played in only 15 England games since March 2006, scoring three goals, but Defoe has backed the Reds' frontman to rediscover his goalscoring form for his country.
The Portsmouth striker said: "Wayne is only going to get better. Maybe you could say the expectation on him has been unfair but he has set such high standards, by doing so well in his career.
"But he is at a great club, he is still young and he is still learning."
then how? can play against liverpool anot?
Another ploy by fergie to keep his players fit for liverpool i think