British light-heavyweight Joshua Buatsi secured a victory yet disappointing beginning to his career under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a tight 10-round fight at the Manchester venue.
But the challenger found success, connecting with powerful single shots in a contest where the styles didn't complement each other, with frequent clinching marring the fight.
Two judges had it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my finest display but what defines champions? They succeed," the victor commented in the arena as he was greeted with negative reactions from the spectators.
The Londoner got back to winning after his initial pro loss - an epic battle with Callum Smith in last winter - to secure a twentieth professional win.
Some ringside observers thought Parker, 31, should have been awarded the win but the British boxer endured the second setback of his 28-bout professional journey.
Buatsi Earns Triumph in Uneventful Affair
The fighter's advancement has stalled in recent times through management issues and long spells of lack of fights.
Previously predicted as the next star of British boxing, he now finds himself trying to fulfil that early promise - perhaps in what seems like a last chance - under fresh management.
He opened tentatively, with neither fighter ready to overcommit in a tentative initial rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in two years ago after breaking his hand in the contest, was making just his second bout at light heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for the favorite, who operated with a protective stance to edge the more effective periods.
The audience's tolerance diminished during constant clinching, with Parker going down multiple occasions during clinches.
The underdog finished the stronger, but several stanzas were challenging to assess. Although, former world champion Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, awarding Buatsi just one round.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Russian champion Bivol ruling the division, the path to championship success - on this evidence - still seems difficult.
Hatton Memorial Fuels Local Rivalry Battle
In the supporting bout, Arthur beat Bradley Rea by close verdict in a outstanding local rivalry fight to capture the European light heavyweight belt.
The venue grew hushed for a profoundly moving memorial before the fight as ten bells sounded in honor of the city's native Hatton, who succumbed at age 46 in recently.
It was the initial significant broadcast match card in the urban center since the passing of Hatton. As the concluding sound disappeared, the stillness gave way to a shout of "there's just one Ricky Hatton".
The competition inside the ropes equaled the sentiment. Arthur was floored by a significant blow directly to the chin in the initial stage, rising shakily to his feet on the eight count.
But the Manchester United-red shorts of Arthur soon pressed ahead again. From the other corner, the opponent - in competitive blue - was damaged soon, significant bruising developing under his eye as the fighters exchanged powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the pace seldom decreased over the full distance.
Arthur barely secured the result with scoring tallies of draw, close margin and wider gap, but both fighters were relentless and brave, all the qualities their hero the legend represented.
