The England Under-20 captain arrived on a season-long arrangement on transfer deadline day but played just once in green and white, starting alongside Paul Hanlon in the 3-0 defeat by Dundee United on October 16.
The 19-year-old was an unused substitute on six other occasions and was omitted from the matchday squad selected for the Premier Sports Cup semi-final against Rangers at Hampden.
Wood was in the stand at Hampden but wasn’t involved in the pre-match celebrations despite other players including injured duo Kyle Magennis and Jamie Murphy and the likes of Sean Mackie and Melker Hallberg joining their team-mates on the pitch after full-time.
Wood returns to the Riverside with a new manager in place in Chris Wilder after Neil Warnock was relieved of his duties at the start of November.
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“The defender, who joined us on a season-long loan in the summer, has gone back to train with the Sky Bet Championship side and will be recalled at the beginning of the January transfer window.
“This decision has been made with Nathan’s development in mind, and to continue our good relationship with Middlesbrough.
“We’d like to thank Nathan for all his efforts during his period with us and we wish him all the best for the future.”