Everton’s bid to land Southampton defender Cuco Martina is currently standing on a knife edge.
Koeman worked with the full-back at the Saints and had been keen on a reunion before the close of the transfer window next week.
But the proposed move is now in jeopardy following injury to Jeremy Pied, which has prompted Claude Puel to rethink allowing Martina to leave.
Koeman’s successor at St Mary’s, has held off on allowing the 26-year-old to join the Blues as competition for Seamus Coleman.
“We will see. It is a problem, it is a question for Cuco also,” Puel told the Southern Daily Echo.
“We will see if the seriousness of the injury, we will see with Cuco stay or the possibility of another player coming.
“We will see the gravity of the injury with Jeremy, it is a problem.”
Koeman, meanwhile, has refuted Everton’s interest in Joe Hart as his Manchester City career appears at an end under Pep Guardiola.
The England goalkeeper was expected to move to Goodison Park following the arrival of Claudio Bravo from Barcelona earlier this week.
But the Everton manager insists that Hart has never been a target for the club.