Jonathan Woodgate gave an update on Boro's injury situation ahead of the match against Charlton Athletic at the Riverside on Saturday (kick-off 3pm).
Paddy McNair is suspended after picking up a fifth booking of the season while Marvin Johnson will serve the final of his three-match ban.
Those two absentees are added to a list of ongoing injury concerns.
"Anfernee Dijksteel will be out for three months," Woodgate confirmed in his pre-match media conference.
"Ryan Shotton and Darren Randolph, we're looking at another four weeks.
"Rudy [Gestede] and Marcus [Browne] are back in training.
"Britt Assombalonga isn't 100% but he should be OK to play. He will feel sore but he wants to play, he's been great for us recently and that's the attitude we need."