Sunderland AFC transfer news: Black Cats thanked for financial help to League One rivals following deadline day deal

The 28-year-old’s contract at the Stadium of Light was set to expire at the end of the season, while he has fallen down the pecking order following the arrivals of Jack Clarke and Patrick Roberts on Wearside.

O’Brien was set to join Doncaster in the summer, yet the deal wasn’t completed in time.

The forward has made 17 League One appearances for Sunderland this season, while he also bagged a hat-trick at Blackpool in the Carabao Cup.

O’Brien has signed for Portsmouth until the end of the season, with Pompey boss Danny Cowley highlighting the player's versatility.

"I think it was an opportunity for us to bring another player in,” Cowley told HampshireLive.

“It is always difficult in January to bring permanents in. We wanted to bring in players that had been playing or had been playing enough football and were physically ready to come in and impact

“We have to thank Sunderland, who have paid some of his money to allow the deal to happen and thank Aiden really for putting himself out there and be willing to take a short-term deal to be willing to play for this wonderful club.”

Cowley also said: “

“We’re really pleased to sign Aiden and from the moment I spoke to him, there was an energy and enthusiasm to join us,” said Cowley

“We’re lucky to be at such a renowned football club because there are so many players who want to come here.

“Aiden brings us many different qualities and can play across the forward line, making penetrative runs.

“He looks after the ball well and links the play, while he can also drive forward and is always a goal threat.

“We’re really looking forward to him being part of this group and he knows quite a few of the lads already, which is important when you arrive on a short-term contract.”

The Black Cats signed Fleetwood midfielder Jay Matete on deadline day and concluded a stunning deal for the return of Jermain Defoe to the Stadium of Light.

A message from the Football Clubs Editor

Our aim is to provide you with the best, most up-to-date and most informative Sunderland AFC coverage 365 days a year.

This depth of coverage costs, so to help us maintain the high-quality reporting that you are used to, please consider taking out a subscription to our new sports-only package here.

Your support is much appreciated. Richard Mennear, Football Clubs Editor