Trio of new faces at Barnet
Derby boss Nigel Clough may rest Jeff Hendrick for Saturday evening's Championship clash with Birmingham at Pride Park.
The 20-year-old has started all but one of the Rams' 17 Championship games but has struggled to reproduce the level of performance he showed last season when he won the club's Young Player of the Year award.
"We either persevere with him or there is a chance he might come out and have a little rest. At 20, we could possibly do more damage leaving him in there," said Clough. "He had a great first season but he is struggling a bit this season. Second seasons are tough for young players like Jeff because everyone knows a bit more about you."
Clough is set to revert back to 4-4-2 for Saturday evening's televised clash, having lined up 4-4-1-1 in the 3-0 defeat to Crystal Palace last weekend.
If Hendrick drops out, Will Hughes and Craig Bryson would be the likely partnership in central midfield with Paul Coutts on the right and Michael Jacobs could keep his place on the left after a lively display at Selhurst Park.
Clough had hoped Jamie Ward would be available after missing nine matches with a hamstring injury but the forward is likely to be overlooked unless he joins in training with the rest of the squad before the end of the week.
Curtis Davies is back in contention to boost Birmingham after missing the last two matches with a niggling ankle injury.
Promising winger Robert Hall, meanwhile, arrived on loan from West Ham late on Thursday afternoon and goes straight into contention for his Blues bow.
There is further positive news regarding on-loan right-back Paul Caddis, who returned to full training on Friday having been sidelined for two months with his shoulder injury. However, Saturday's game is expected to come too soon.
Left-back David Murphy underwent a knee operation on Thursday night which rules him out for the foreseeable future, joining fellow defender Stephen Carr (knee) on the sidelines.
Midfielder Keith Fahey is expected to remain unavailable having been granted compassionate leave for an indefinite period.
Stevenage centre-back Iro, 27, and Brighton striker Barker, 21, will stay on loan at Underhill until 22 January.
Holwijn is a 32-year-old Dutch winger who has signed on non-contract terms.
"We're delighted to have got Andy in on loan to further strengthen our defensive line," said Bees joint head-coach Mark Robson to the club's official website.
"George potentially has a lot to offer us. We hope he'll get the opportunity to show his qualities and to give us another option up front."