England's Owen Hargreaves has suffered a setback to his World Cup hopes after a scan on his shin injury proved inconclusive.
Hargreaves had been hoping to get the all-clear after suffering the injury early in the victory against Argentina.
But he now needs more treatment and may require another scan.
He is definitely out of the game against Nigeria on Wednesday and could struggle to make England's clash in the last 16 if they qualify.
It will be a major disappointment for Hargreaves if he is out for a lengthy spell after winning a place in the starting line-up with impressive performances in friendlies against South Korea and Cameroon.
"It is unfortunate because I have never really had an injury before in my life and I will just have to keep my fingers crossed," he said on Monday.
Sinclair to come in
The FA's head of communications, Paul Newman, added: "The results of the scan were inconclusive and showed no specific damage.
"It may have to be repeated, but in the meantime Owen will continue to be treated, when his progress will be assessed."
Trevor Sinclair, who was a successful deputy for Hargreaves against Argentina, will continue in the side against Nigeria.
This is likely to be the only change from the starting line-up against Argentina.
But there are suggestions defender Ashley Cole may be rested to avoid picking up another yellow card that would earn him a suspension if England qualify for the last 16.
England's preparations for their crunch World Cup game against Nigeria could
be hit by a tropical storm.
The remnants of typhoon Noguri is on a north-easterly heading from the Pacific
"The good news is that by the
time of the match the thundery downpours will be out of the way," said PA Weathercentre spokesman Michael Dukes.
"The bad news is that high temperature and oppressive humidity may suit the
"If anything, it will be hotter and more humid than it has been up until