Sylvain Legwinski will be out for a number of weeks after scans shown that his foot has been badly bruised and the club will take specialist advice before proceeding.
The midfielder came off injured in the 26th minute of the Luton match after a block tackle on Louis Emanuel.
Jim told the club site: "We were hoping that Sylvain would be back for the Plymouth game but the injury is more serious than that.
"He made a block tackle in the Luton game and we thought it was just bruising on the foot but the scans have revealed quite extensive bone bruising.
"Our medical team are now in conversation with a specialist and we will be sending the scans on to get their view and then take it from there.
"We will know more next week but it looks as though Sylvain will be out for a few weeks at least."
It is likely that either George O'Callaghan or Gavin Williams will join Owen Garvan in the centre of midfield for the next match at home to Plymouth.
Get the fastest and most comprehensive Ipswich Town news service at ipswichtown.footballlatest.co.uk.