After the Whites came close to closing a deal for O'Brien last summer, Leeds' chances of Town accepting a fresh bid for the talented player were set to be upset by the South Yorkshire side's promotion bid.
But with the Terriers falling six points shy of an automatic promotion spot and falling to a 1-0 defeat in the Championship Play-Off final to Nottingham Forest, United will find it much easier to prise O'Brien from the second-tier club should they choose to continue their pursuit.
What is happening to former Leeds United star Raphinha at Barcelona amid latest farce and deadline
Leeds United plot ‘double hit’ for attacking duo, Whites ‘weighing up’ bargain defender swoop
Leeds United news: Raphinha set to miss La Liga opener as Whites eye MLS left-back
Leeds United in ‘direct talks’ over swoop for rising star as Jesse Marsch makes ‘transfer decision’
Leeds United ‘express interest’ in transfer as ‘decision made’ over player’s future
Who is he?
Born in Colchester, O'Brien began his football career at the Huddersfield Town Academy where he has played ever since, though he earned 40 appearances on loan at Bradford City in the 2018/2019 season.
Where does he play?
A versatile midfielder by trade, O'Brien best suits a number eight role but can also play as a number 11, a number 10 and a number 7. He also succeeds in wide areas as a full-back or wing-back.
Why do Leeds United want him?
O'Brien is widely considered a sparkling all-rounder with strength in every aspect of his game. Foremost of these is a fantastic engine which has helped to power Town to an impressive 50% Championship win rate this season.
With four full EFL seasons under his belt, the 23-year-old boasts experience and has taken on the armband for the John Smith's Stadium outfit a number of times.
He is said to be a conscientious football player, with Town boss Carlos Corberan having praised O'Brien's humility and 'limitless' potential.
The midfielder's training under Corberan, who was previously on the staff of former United boss Marcelo Bielsa, is a significant draw for the Leeds as O'Brien would slot neatly into a Whites squad which still bears attributes of the Argentine's style of play.
Where would O'Brien fit in at Elland Road?
For many months, central midfield has been an area of worry for Leeds United, and the concern could deepen this summer with the potential departure of Kalvin Phillips.
After some spectacular Adam Forshaw performances this season, Whites chairman Andrea Radrizzani looked to have been vindicated by his suggestion that the midfielder's return from injury would feel like a new signing but the Liverpudlian's fractured kneecap has sown fresh doubt as to the player's continual ongoing fitness.
Meanwhile, Mateusz Klich hasn't looked entirely convincing under the Jesse Marsch regime and the responsibility a full Premier League season seems a little much to put on the shoulders of 19-year-old Lewis Bate, for all the promise he showed for the senior team in the latter stages of the season.
If United can succeed in bagging a talented Championship centre-mid for a reasonable fee then it'll be a significant weight off the minds of the Elland Road faithful.