Didier Ndong has completed his loan move to Premier League side Watford.
The Gabon international midfielder spent this afternoon completing his medical in London ahead of his loan deal until the end of the season.
The deal could turn permanent in the summer provided certain criteria including the number of appearances made are met.
Sunderland have confirmed the Hornets "will have an obligation to purchase the player, should certain criteria be met."
The deal could be worth around the £9million mark if the move becomes permanent.
Sunderland are understood to have secured a loan fee as part of the loan deal.
Speaking last night, Coleman admitted Ndong was on the verge of a move but said the conditions on the bid from earlier in the window had improved and that he was 'excited' at the prospect of Ovie Ejaria's arrival in his place.
Coleman said: "Ndong is going to Watford, he’s made it clear that he wanted to be back in the Premier League.
"The deal suited us this time, there’s stipulations in the contract that could make it permanent, but he could come back. We’re bringing one in to replace him, the boy from Liverpool, Ovie Ejaria, until the end of the season.
"I’m really excited about that.
"We shouldn’t worry too much about losing Ndong because we haven’t really had him all season if you look at his gametime. Ovie [Ejaria] is a good player and he’ll be a good addition."
Having started his senior career with Tunisian club CS Sfaxien, Ndong switched to Lorient three years ago in Ligue 1, playing 54 times for the French side before his move to Sunderland for a £13.6million fee in the summer of 2016.