ROTHERHAM United loan goalkeeper Jamal Blackman has returned to parent club Chelsea for treatment and the Millers admit they don't know when they will see him again.
The 27-year-old missed last Saturday's 2-1 Championship win over Preston North End because of an ankle complaint and headed back to London.
He will be looked after by the Premier League outfit's medical team but there is no guarantee he will be recover during the international break in time for Rotherham's next match, at Swansea City, on November 21.
"The problem has been going on for a few weeks now, since before the Nottingham Forest game," manager Paul Warne said.
"I am not sure how long Jamal will be out for. He will have a scan and he is having it injected and everything."
Blackman had played last Wednesday in the 1-0 defeat to Luton Town and had been clearly troubled by his ankle as he turned in a poor kicking performance.
Young Swede Viktor Johansson made his debut against Preston and staked his claim to be Rotherham's number one with an impressive display.
Warne had been looking to bring in a free-agent midfielder after the broken-leg loss of Shaun MacDonald but instead chose to sign a third shot-stopper on the eve of the Lilywhites showdown.
Kieran Sadlier before going off on Saturday
Josh Vickers filled the 25th and final place in Rotherham's squad and was on the bench at AESSEAL New York Stadium at the weekend.
"I couldn't go into a Championship game with one goalkeeper," the boss said.
The Millers have other injury concerns, with full-back Joe Mattock and Billy Jones missing out against Preston because of hamstring and knee problems respectively and winger Kieran Sadlier limping off after 23 minutes after rolling his ankle.
All three are expected to be out for two to three weeks.
"Luckily, we haven't got to rush Sads," Warne said. "He is a fit kid anyway and without having to prep for a game (next weekend) we can take our time."
MacDonald, winger Chiedozie Ogbene (knee) and centre-half Clark Robertson (foot) are all out until the New Year.
Warne made six changes last Saturday and saw his 19th-placed side respond by ending Preston's unbeaten away record.