UK light heavyweight Joshua Buatsi earned a win yet underwhelming debut to life under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a split decision in a competitive 10-round bout at the boxing arena.
But the challenger found success, landing some telling clean blows in a contest where the techniques didn't complement each other, with frequent clinching spoiling the action.
Two judges judged it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my finest display but what do champions do? They win," the victor stated in the ring as he was met by disapproval from the audience.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in last winter - to secure a twentieth professional win.
Some ringside observers believed Parker, thirty-one, deserved the victory but the British boxer experienced the second setback of his 28-match career.
The Champion Secures Victory in Uneventful Affair
The fighter's advancement has plateaued in recent times through management issues and extended periods of lack of fights.
Previously predicted as the future of British boxing, he now finds himself trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under recent support.
He opened tentatively, with both competitors willing to overcommit in a cagey initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second appearance at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for Buatsi, who worked behind a tight guard to narrowly win the better rounds.
The crowd's patience diminished amid regular grabbing, with the challenger slipping to the canvas several times during close exchanges.
The underdog finished the stronger, but multiple periods were challenging to assess. However, ex-champion Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, scoring for Buatsi just one round.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - judging by this showing - still appears challenging.
Hatton Homage Motivates All-Manchester Contest
In the supporting bout, Lyndon Arthur defeated Rea by split-decision in a terrific local rivalry battle to capture the European light-heavyweight title.
The arena fell silent for a profoundly moving tribute prior to the bout as 10 bells rang in memory of the city's native Hatton, who succumbed aged 46 in last month.
It was the first major televised fight night in the location since Hatton's death. As the final chime faded, the silence gave way to a shout of "there's only one Ricky Hatton".
The fighting inside the ropes matched the sentiment. Arthur was floored by a powerful punch directly to the face in the second round, standing uncertainly to his feet on the eight count.
But the Manchester United-red shorts of Arthur soon came forward again. On the opposite side, the opponent - in rival City blue - was marked up soon, heavy swelling developing under his orbital area as the pair traded punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with effective uppercuts as the pace seldom decreased over 12 rounds.
The victor edged the verdict with judges scorecards of 114-114, 115-113 and clearer margin, but both fighters were persistent and courageous, exactly what their idol the legend stood for.
