HITC Sport understands that Manchester City are ready to sanction an extension through to the end of the season.
The 22-year-old joined Boro at the end of last month, signed just in time to make his debut in the League Cup win at Manchester United.
He has been involved in every league match since and Boro boss Aitor Karanka is hoping to extend the deal for the rest of the season.
HITC Sport understands that Manchester City have been happy with Zuculini’s involvement and they are ready to sanction an extended deal.
With Zuculini set to remain on Teesside for the foreseeable future, Boro are set to agree to Jack Stephens moving back to Southampton – as he has failed to command much football since his summer loan switch.
It will be increasingly difficult for anyone on the fringes of the side at the Riverside to force their way into starting contention, with Boro currently perched fourth in the Championship standings, four points adrift of the automatic promotion spots.