Doncaster thought they had their man after agreeing on a loan deal with Sunderland.
Confident of confirming the deal, Sunderland sent the wrong form to Doncaster for O'Brien and by the time they had amended it, deadline day had passed.
Sitting bottom of the table with no wins from five, fans are fearing the worst, and rightly so...
Doncaster rivals Rotherham won the race to sign Will Grigg from Sunderland.
The Northern Ireland forward joined on a loan deal for the Millers and it's safe to say we'll be hearing THAT song.
It was on, then it was off and then it was confirmed.
Saul Niguez will be playing at Stamford Bridge this season. The midfielder moves from Atletico Madrid on a loan deal which could be made permanent next summer.
Barcelona have continued the trend of selling their best players on deadline day. Two years after leaving for £107million to Barca, Griezmann has rejoined Atletico. They have an agreement on bringing him back permanently for £34.4million.
Not exactly a new signing but it's a big moment...
Is Rafael Benitez trying to become the new Harry Redknapp?
Rondon is reuniting with Benitez after Everton picked him up on a free transfer.
The pair previously worked together at Newcastle United and Chinese club Dalian Pro.
Linked with Reading, the former England international was unable to agree on terms. Spurs fans, what's your thoughts?