British light-heavyweight Joshua Buatsi earned a win yet disappointing debut to his career under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a close 10-round fight at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective single shots in a match where the approaches didn't complement each other, with constant grabbing spoiling the contest.
Two judges judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my finest display but what do champions do? They win," the victor said in the ring as he was met by disapproval from the crowd.
The Londoner got back to winning after his maiden career setback - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Various analysts felt Parker, 31, should have been awarded the win but the British boxer endured the second setback of his 28-match professional journey.
Buatsi Earns Win in Slow Affair
The fighter's advancement has stalled in recent times through contract problems and considerable time of inactivity.
Previously predicted as the next star of British boxing, he now is positioned trying to fulfil that early promise - possibly in what appears to be a last chance - under fresh management.
He began cautiously, with the two boxers willing to overcommit in a tentative opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after damaging his hand mid-fight, was making just his second fight at light-heavyweight.
By the middle rounds, the underdog had kept it close, causing problems for Buatsi, who utilized a protective stance to barely take the more effective rounds.
The audience's tolerance diminished amid frequent holding, with Parker going down several times during grappling.
Parker finished the stronger, but several stanzas were challenging to assess. Although, ex-champion Carl Frampton - working with Dazn - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
Buatsi advances, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - based on this performance - still seems difficult.
Hatton Tribute Motivates Manchester Derby Contest
In the co-main event, Arthur overcame Rea by divided decision in a terrific all-Manchester contest to secure the European light heavyweight belt.
The arena fell silent for a deeply poignant homage ahead of the contest as 10 bells rang in remembrance of the city's native Ricky Hatton, who died at age 46 in recently.
It was the initial significant broadcast boxing event in the urban center since the passing of Hatton. As the last bell disappeared, the stillness gave way to a chant of "only one Ricky Hatton".
The competition during the bout equaled the feeling. The eventual winner was sent to the canvas by a left hook flush on the jaw in the initial stage, standing uncertainly to his feet on the count of eight.
But the red-colored shorts of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was marked up quickly, heavy swelling appearing under his eye as the duo exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with powerful upward punches as the intensity hardly diminished over twelve rounds.
The victor barely secured the decision with scoring tallies of draw, narrow lead and wider gap, but each competitor were relentless and brave, all the qualities their hero Hatton represented.
