Aiden O'Brien spent almost a decade at Millwall, scoring 44 goals in 226 appearances between 2011 and 2020.

O'Brien burst on the scene as an 17-year-old, making his in a League Cup defeat to Wolves, but wouldn't feature again for almost three seasons, gaining senior experience whilst on loan at Hayes & Yeading, Crawley, Aldershot and Torquay.

The appointment of Neil Harris - O'Brien's former U21s boss at The Den - at the end of 2014-15 saw the attacker finally given his first-team opportunity - scoring twice in 20 appearances, but couldn't save the Lions from relegation.

However, the Republic of Ireland international would become a regular on the scoresheet in League One, striking 23 times across two seasons as Millwall won promotion back to the Championship at the second time of asking following a play-off final victory over Bradford in May 2017 - with O'Brien playing 70 minutes at Wembley.

 

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The Lions Academy product would continue as a regular during the first part of the 2017-18 campaign, but injuries and the arrival of Ben Marshall saw O'Brien featured just 10 times after Christmas.

O'Brien scored twice at the beginning of the following season, which led to an international call-up Ireland, where he'd notch on his debut against Poland, but he'd net just twice more in the final nine months of that campaign - although one came in the FA Cup quarter-final loss to Brighton at The Den.

2019-20, O'Brien's last in SE16, was perhaps his most disappointing. His opportunities were limited, making just eight league starts, and although he scored a cluster of goals around the festive period, the likes of Matt Smith, Tom Bradshaw and Jon Dadi Bodvarsson were often preferred - with his final outing coming against Bristol City in late-February.

Upon the expiration of his contract, O'Brien made the switch up to Sunderland on a two-year deal, dropping down to League One for the first time in four seasons.

The Black Cats have been impressive this term, but O'Brien hasn't yet nailed down a regular place in Phil Parkinson's starting XI. He's started half of their League One matches and is still waiting for his first league goal in Sunderland colours - although he did score in their 8-1 win over Aston Villa's U21s in the EFL Trophy last month. That remains O'Brien's only in his nine appearances in all competitions, and he was an unused substitute in Saturday's 3-1 defeat to Portsmouth. It hasn't gone to plan for the former Lions man, but the attacker has gone a proven goal-record at this level and is still settling into his new surroundings.