UK light-heavyweight Joshua Buatsi made a winning yet unimpressive start to his career under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a competitive ten-round bout at the Co-op Live Arena.
But Parker found success, delivering effective single shots in a contest where the styles failed to mesh, with frequent clinching marring the fight.
Two judges had it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my finest showing but how do champions respond? They prevail," Buatsi stated in the arena as he was greeted with disapproval from the crowd.
The British fighter bounced back after his maiden career setback - an epic battle with Callum Smith in February - to claim a twentieth professional win.
Several boxing experts felt the challenger, 31, should have been awarded the victory but the Derbyshire fighter endured the second defeat of his 28-fight career.
Buatsi Earns Victory in Dull Encounter
The fighter's advancement has stalled in the past few years through management issues and extended periods of inactivity.
Once tipped as the future of UK boxing, he now is positioned trying to achieve expectations - possibly in what seems like a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter willing to overcommit in a calculated early stages.
Parker, whose single earlier setback came at super middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was making just his second appearance at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for the favorite, who utilized a solid defense to edge the cleaner stanzas.
The crowd's patience wore thin because of constant clinching, with Parker falling to the floor several times during close exchanges.
The underdog ended stronger, but many rounds were difficult to score. Nevertheless, ex-champion Carl Frampton - providing analysis for Dazn - had it particularly wide for the challenger, giving Buatsi just only one stanza.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Memorial Fuels Local Rivalry Contest
In the secondary fight, Arthur defeated Rea by close verdict in a terrific Manchester vs Manchester fight to win the European light heavyweight belt.
The stadium fell silent for a extremely emotional tribute ahead of the contest as a bell ceremony sounded in remembrance of local hero Ricky Hatton, who passed away aged 46 in recently.
It was the first major televised fight night in the urban center since Hatton's death. As the concluding sound ended, the silence transitioned to a roar of "there's just one Ricky Hatton".
The competition during the bout equaled the emotion. The eventual winner was floored by a powerful punch flush on the jaw in the early round, getting up unsteadily to his feet on the count of eight.
But the traditional red equipment of the fighter soon advanced again. From the other corner, the opponent - in competitive blue - was marked up early, heavy swelling forming under his eye as the pair exchanged punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with effective uppercuts as the action rarely dropped over the full distance.
The victor barely secured the verdict with official scores of draw, narrow lead and wider gap, but both fighters were determined and brave, exactly what their idol Hatton embodied.
