British light heavyweight Joshua Buatsi earned a win yet disappointing debut to his career under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a competitive ten-round contest at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful individual punches in a match where the techniques never quite clicked, with frequent clinching spoiling the contest.
Two judges judged it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my finest display but what defines champions? They win," Buatsi stated in the ringside as he was greeted with negative reactions from the audience.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with Callum Smith in last winter - to earn a twentieth professional win.
Some ringside observers felt the challenger, 31, deserved the victory but the British boxer experienced the second setback of his 28-fight career.
The Champion Claims Victory in Uneventful Encounter
Buatsi's progress has stalled in the past few years through promotional disputes and long spells of lack of fights.
Earlier forecast as the rising talent of British boxing, he now stands trying to realize his potential - maybe in what seems like a last chance - under recent support.
He began cautiously, with both competitors willing to take risks in a calculated initial rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in two years ago after damaging his hand during the bout, was making just his second bout at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, causing problems for the favorite, who worked behind a protective stance to narrowly win the cleaner periods.
The audience's tolerance wore thin amid frequent holding, with the challenger slipping to the canvas various instances during close exchanges.
Parker ended stronger, but several stanzas were challenging to assess. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just a single round.
The victor advances, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Hatton Memorial Inspires All-Manchester Battle
In the supporting bout, Arthur overcame Rea by split-decision in a terrific all-Manchester battle to capture the continental belt.
The arena grew hushed for a deeply poignant homage before the fight as ten bells rang in remembrance of the city's native Hatton, who died aged 46 in recently.
It was the premier televised boxing event in the location since the passing of Hatton. As the final chime disappeared, the quiet gave way to a roar of "there's just one Hatton".
The action within the ring reflected the feeling. Arthur was knocked down by a left hook squarely on the jaw in the second round, standing uncertainly to his footing on the referee's count.
But the Manchester United-red shorts of Arthur soon advanced again. On the opposite side, the opponent - in competitive blue - was injured early, noticeable damage forming under his orbital area as the duo landed punishing blows.
Rea, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with powerful upward punches as the intensity seldom decreased over twelve rounds.
Arthur narrowly won the result with scoring tallies of draw, 115-113 and 115-112, but both fighters were persistent and courageous, exactly what their hero the legend embodied.
