Middlesbrough defender Robert Huth is to see a specialist after suffering a setback following surgery on his ankle.
The German defender, 22, signed from Chelsea at the start of last season but only made 12 starts due to the injury.
Central defenders Jonathan Woodgate and Emanuel Pogatetz and Matthew Bates are also on Boro's long-term injury list.
"We're in a phase where we're getting an incredible number of things thrown at us, none of them," said Boro boss Gareth Southgate.
The Boro boss added: "He's had a bit of a setback. He's gone to see a specialist to see what's happened."
Boro have lost their opening two Premier League games of the season.