The 26-year-old, who had rejected the Millers' overtures regarding a new deal - with his contract expiring this summer – attended Boro’s win over Watford on Saturday.

The Gateshead-born schemer, formerly of Newcastle United, was the subject of a bid from the Teessiders earlier this window, which was rejected by Rotherham.

The Riverside Stadium outfit have maintained their interest and have now finalised a deal to sign Barlaser with the South Yorkshire club.

Speaking about Barlaser after Saturday’s game, Boro boss Michael Carrick said: “I’ve been aware of him. I’ve known of him for a while, with him being at Newcastle and coming through.

"There are certain styles of players that catch your eye, and that you can understand what they can bring in certain situations and certain positions. He’s always one that I’ve had an eye on.

“It comes down to a number of things. Alex (Mowatt) has been around it, and he’s done well when he’s come on and played, but we understand what kind of positions we’ve wanted to strengthen and what kind of players and things we’re looking for in certain positions.

“It comes down to the character and attitude, and what they can bring to the group, and as a midfielder for how we want to play, Dan fits that perfectly. When we had the chance and the opportunity to do it, I’m delighted with the way things have gone.

"I’m looking forward to working with him and trying to help him improve. He’s delighted to have the opportunity to come and learn, and be part of the team.

“It’s not just about the pitch, and bringing a certain player in, it’s about what goes around the whole situation. He fits. I’ve said before that we’re really specific about what we’re after in certain positions, and it’s not just about taking a good player because they’re a good player. There’s more behind it than that, and Dan fits that perfectly."

The move would see him link up again with ex-Millers midfielder Matt Crooks and a former loanee in Ryan Giles.

Boro also have an interest in Millers striker Chiedozie Ogbene, who has also shown no inclination to sign a new deal with his existing contract ending in June.

Ogbene has rival suitors at second-tier level.

The Millers brought in a forward earlier this week in the shape of Norwich City frontman Jordan Hugill and followed up with the signing of West Ham midfielder Conor Coventry, who has joined on loan for the rest of the campaign.

On the incoming front, Rotherham have also brought in Brentford winger Tariqe Fosu, Leeds United loanee Leo Hjelde and ex-Cardiff and Reading centre-half Sean Morrison this month.

Boro have signed Aston Villa striker Cameron Archer on loan for the remainder of the season.

Rotherham United transfer news: Championship rivals Middlesbrough FC complete signing of Millers midfielder Dan Barlaser