UK light heavyweight Joshua Buatsi secured a victory yet disappointing beginning to his career under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a majority decision in a tight ten-round contest at the boxing arena.
But the challenger found success, landing some telling clean blows in a fight where the styles never quite clicked, with frequent clinching spoiling the action.
Two judges scored it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my finest showing but what defines champions? They win," the victor stated in the ring as he was faced negative reactions from the audience.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to claim a 20th pro success.
Various analysts believed the challenger, 31, merited the decision but the British boxer experienced the second loss of his 28-fight career.
Buatsi Earns Triumph in Dull Match
His career development has stalled in recent times through management issues and considerable time of inactivity.
Earlier forecast as the next star of British boxing, he now is positioned trying to fulfil that early promise - possibly in what feels like a final roll of the dice - under recent support.
He started carefully, with neither fighter prepared to be aggressive in a tentative opening few rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in 2022 after suffering a hand injury mid-fight, was competing in only his second fight at light-heavyweight.
By the halfway stage, Parker had made it competitive, making life awkward for the favorite, who operated with a tight guard to edge the better stanzas.
The audience's tolerance decreased amid regular grabbing, with the challenger going down various instances during clinches.
Parker ended stronger, but many rounds were challenging to assess. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, awarding Buatsi just one round.
The victor moves on, but with the likes of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - based on this performance - still looks steep.
Hatton Memorial Motivates Local Rivalry Fight
In the secondary fight, Lyndon Arthur defeated Bradley Rea by split-decision in a outstanding Manchester vs Manchester contest to capture the European light-heavyweight title.
The arena fell silent for a extremely emotional homage before the fight as 10 bells rang in honor of the city's native Ricky Hatton, who died 46 years old in recently.
It was the initial significant broadcast boxing event in the city since the passing of Hatton. As the concluding sound disappeared, the stillness became a roar of "only one Hatton".
The competition inside the ropes matched the feeling. The eventual winner was sent to the canvas by a left hook flush on the face in the early round, rising shakily to his position on the eight count.
But the red-colored equipment of Arthur soon advanced again. From the other corner, the opponent - in competitive blue - was marked up soon, noticeable damage developing under his orbital area as the pair traded hard punches.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over twelve rounds.
Arthur narrowly won the decision with scoring tallies of even score, 115-113 and 115-112, but each competitor were determined and brave, all the qualities their hero Hatton stood for.
