British light heavyweight Joshua Buatsi made a winning yet disappointing start to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a majority decision in a tight ten-round fight at the Manchester venue.
But Parker had his moments, landing some telling clean blows in a contest where the styles never quite clicked, with excessive holding spoiling the fight.
The officials had it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my best performance but what do champions do? They prevail," the victor stated in the ringside as he was met by disapproval from the crowd.
The Londoner got back to winning after his maiden career setback - an thrilling contest with his previous opponent in February - to secure a twentieth professional win.
Several boxing experts felt Parker, thirty-one, should have been awarded the decision but the British boxer experienced the second loss of his 28-bout career.
Buatsi Secures Triumph in Slow Match
Buatsi's progress has plateaued in the past few years through management issues and extended periods of inactivity.
Previously predicted as the future of the British fight scene, he now is positioned trying to fulfil that early promise - perhaps in what feels like a last chance - under fresh management.
He opened tentatively, with neither fighter willing to overcommit in a tentative initial rounds.
The challenger, whose only previous defeat came at super middleweight against John Ryder in 2022 after breaking his hand in the contest, was competing in only his second fight at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who utilized a protective stance to barely take the cleaner periods.
The crowd's patience diminished because of regular grabbing, with the challenger falling to the floor several times during close exchanges.
The underdog finished the stronger, but many rounds were difficult to score. However, former world champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the likes of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still looks steep.
Ricky Hatton Tribute Fuels Local Rivalry Battle
In the co-main event, Arthur beat Rea by divided decision in a terrific all-Manchester contest to win the European light heavyweight title.
The stadium became quiet for a deeply poignant memorial prior to the bout as 10 bells tolled in remembrance of local hero Ricky Hatton, who passed away at age 46 in September.
It was the premier televised fight night in the urban center since Hatton's passing. As the concluding sound ended, the stillness became a chant of "only one Hatton".
The competition inside the ropes matched the emotion. The eventual winner was floored by a left hook squarely on the chin in the early round, rising shakily to his footing on the referee's count.
But the traditional red attire of Arthur soon came forward again. On the opposite side, Rea - in rival City blue - was damaged early, heavy swelling forming under his face as the pair landed punishing blows.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace hardly diminished over twelve rounds.
The victor narrowly won the decision with scoring tallies of 114-114, 115-113 and 115-112, but each competitor were determined and full of heart, all the qualities their idol the legend represented.
