British light heavyweight Joshua Buatsi made a winning yet disappointing beginning to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
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 had his moments, connecting with powerful individual punches in a match where the techniques never quite clicked, with frequent clinching spoiling the fight.
The scoring judges scored it 96-94 to the winner, with the remaining official a even score.
"It wasn't my best display but what do champions do? They win," the victor commented in the ringside as he was greeted with negative reactions from the audience.
The Londoner returned to winning ways after his first professional defeat - an epic battle with his previous opponent in last winter - to secure a 20th pro success.
Several boxing experts felt Parker, 31, merited the victory but the British boxer experienced the second setback of his 28-fight career.
Buatsi Claims Victory in Slow Encounter
His career development has slowed in recent times through management issues and extended periods of lack of fights.
Earlier forecast as the next star of UK boxing, he now stands trying to realize his potential - perhaps in what appears to be a last chance - under recent support.
He started carefully, with neither fighter willing to overcommit in a calculated initial rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in two years ago after damaging his hand in the contest, was participating in his second fight at light heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for the favorite, who utilized a solid defense to barely take the better stanzas.
The crowd's patience wore thin amid frequent holding, with the challenger falling to the floor various instances during clinches.
The underdog ended stronger, but several stanzas were hard to judge. Although, previous titleholder the boxing analyst - working with Dazn - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi advances, but with the caliber of hard hitter David Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Memorial Fuels All-Manchester Contest
In the co-main event, Arthur overcame Bradley Rea by divided decision in a outstanding Manchester vs Manchester fight to capture the European light heavyweight championship.
The venue became quiet for a profoundly moving tribute before the fight as a bell ceremony tolled in remembrance of the city's native Hatton, who succumbed at age 46 in last month.
It was the premier televised fight night in the city since the passing of Hatton. As the final chime faded, the stillness transitioned to a roar of "only one Ricky Hatton".
The fighting within the ring equaled the emotion. The eventual winner was floored by a powerful punch directly to the face in the early round, rising shakily to his position on the eight count.
But the traditional red shorts of Arthur soon advanced again. From the other corner, Rea - in competitive blue - was injured early, noticeable damage appearing under his orbital area as the fighters landed punishing blows.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with effective uppercuts as the pace rarely dropped over twelve rounds.
Arthur barely secured the result with judges scorecards of draw, close margin and clearer margin, but the two athletes were determined and full of heart, all the qualities their hero the legend embodied.
