Swindon Town loanee Brad Smith has returned to parent club Liverpool for treatment on a knee injury, which could keep him out for several weeks.
The 20-year-old left-back joined the League One club on a season-long loan last week and made his debut in Saturday's victory over Scunthorpe.
But he was forced off with the injury in Tuesday's League Cup win at Luton.
"He probably won't feature for a few weeks," Swindon manager Mark Cooper told BBC Wiltshire.
"We think he's got a grade one medial strain. We're waiting for a scan result from Liverpool but he certainly won't be able to feature for a few games."
The Town boss went on to confirm that may have the chance to bring in cover before Saturday's league fixture at Crawley.
"We've maybe got the option of bringing a natural left-footer in," he added. "I've spoken to the chairman about that so we'll see what happens over the next few hours and next day.
"We've got Ben Gladwin who can slot into midfield and [forward] Andy Williams who came on and played really well the other night, so we've got a few options.
"But with the form [full-back] Nathan Byrne is in, we're loathed to switch him back to the left side, so we've got a bit of thinking to do."