Martin in line to face Magpies
The Rams are also closing in on a loan deal for Arsenal's 18-year-old French forward Gilles Sunu now that a return to Pride Park for Everton striker James Vaughan is looking less likely.
Martin (pictured) was not involved in Millwall's victory over Norwich City on Saturday but the 24-year-old was at Bramall Lane to watch Derby's 1-1 draw with Sheffield United.
His permanent move fell through just before the transfer window closed a week ago.
Millwall accepted a bid worth £200,000 for Martin, whose contract with them expires at the end of the season, and now he will sign on loan to the end of the season when a permanent deal will be sealed.
"Everything is agreed. The window opens on Tuesday morning and we can register him up to noon as an emergency loan," said manager Nigel Clough.
"He'll be in the 18 against Newcastle United tomorrow night if it gets sorted.
"It will be a loan to the end of the season but the permanent deal is agreed. It will be ideal to get him for the next two or three months so he can settle in."
Martin impressed playing for Millwall in two FA Cup games against the Rams last month. His record for the Lions is nine goals in 88 appearances.
Arsenal are currently trying to sort out clauses in Sunu's contract and the Rams are just waiting for the go-ahead from the Gunners to take the youngster on loan.
"We are still after him, it's still a possibility," said Clough.
"Tom Glick (chief executive) is in touch with Arsenal every few days. The player is happy to come and we have agreed the wages with Arsenal, so it is just a case of them getting it sorted."
Sunu can play up front or from the right.
He was a member of Arsenal's FA Youth Cup-winning side last season and has made two appearances for the first team this season. He started the Carling Cup victory over West Bromwich Albion and was a substitute in the Champions' League clash against Olympiakos in Greece.
Vaughan's brief loan spell at Derby earlier this season was cut short by a knee injury.
The 21-year-old was not in Everton's 18 on duty against Liverpool in Saturday's Merseyside derby. They started with Louis Saha up front and Tim Cahill playing just off him. Strikers Yakubu and Victor Anichebe came off the bench late in the game.
When asked about a possible return for Vaughan, Clough said: "Nothing has changed there, so it is unlikely we will get James now.
"But if we can get Sunu, it would be a direct replacement."
Coventry City are now being linked with Vaughan who has slipped back down the pecking order of strikers at Goodison.
