Youngster Trai Hume became Sunderland' s first January signing, with the Black Cats paying a six-figure sum to sign the talented right back from Linfield.
And now, Danny Batth has opted to join the Black Cats on an 18-month deal, becoming the second signing of the January transfer window after Hume and Sunderland have not paid a fee for the defender.
Johnson says that he has twice signed to sign Batth in the past, who has twice promotion from League One.
The Sunderland head coach has cited his leadership qualities as potentially crucial for the second half of the season.
But who else have Sunderland been linked with?
Here, we take a look:
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1. Trai Hume
The young right-back became Sunderland's first signing of the window and has made Lee Johnson's bench in recent weeks. He is yet to make his senior debut for Sunderland yet, however. Photo: Soccrates Images
2. Macauley Bonne
Sunderland and Wigan Athletic have been linked with Queens Park Rangers striker Macauley Bonne this month Photo: Ashley Allen
3. Danny Batth
Danny Batth is now a Sunderland player after the defender signed an 18-month deal at the Stadium of Light. Photo: Robbie Jay Barratt - AMA
4. Cameron Archer
One player that has recently been linked with a move to Sunderland is Cameron Archer from Aston Villa. However, Steven Gerrard apparently wants to keep the young striker at Villa Park. Photo: Clive Brunskill