Sunderland manager Lee Johnson managed to bolster his squad yesterday by sealing last-gasp loan moves for Leon Dajaku and Thorben Hoffmann.
Meanwhile, the Black Cats also opted to wave goodbye to two players.
Jack Diamond joined Harrogate Town on a temporary basis on Tuesday whilst Will Grigg sealed a loan switch to Rotherham United.
It seemed as if Aiden O'Brien was also set to leave Sunderland yesterday as he was on the verge of completing a move to fellow League One side Doncaster Rovers.
However, this particular deal collapsed during the closing stages of the transfer window.
The reasoning behind why the winger was unable to complete a switch to Doncaster has now been revealed.
According to the Doncaster Free Press, Richie Wellens' side were unable to process a move due to the fact that Sunderland provided them with the wrong form to sign.
By the time that this particular issue was rectified, the deadline for the submission of the right paperwork had passed.
Doncaster were also believed to be interested in a move for Sunderland forward Grigg.
However, despite matching the highest wage offer for the Northern Ireland international, Rovers missed out on securing his services as Rotherham won the race for his signature.
O'Brien has struggled for consistency during his time at Sunderland.
The winger was only able to find the back of the net on six occasions last season despite making 40 appearances for the Black Cats in all competitions.
Considering that he is currently behind Aiden McGeady in the pecking order at the Stadium of Light, O'Brien may find it difficult to force his way into the club's starting eleven in the coming months.
GIVEMESPORT's Joshua Cole says...
Having missed out on the opportunity to seal a temporary move to Doncaster as a result of an error by Sunderland, O'Brien will now need to put this disappointment behind him.
Whilst the winger's displays during the previous campaign left a lot to be desired, he did recently showcase his talent in the club's League Cup clash with Blackpool.
O'Brien managed to record a WhoScored match rating of 9.17 in this particular showdown as he scored a hat-trick at Bloomfield Road to secure victory for the Black Cats.
Providing that he is able to build upon this display in the coming months, O'Brien could potentially become a key player for a Sunderland side who will be looking to launch a push for promotion this season.
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