UK light-heavyweight Joshua Buatsi made a winning yet underwhelming start to his career under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a majority decision in a tight 10-round contest at the boxing arena.
But Parker found success, landing some telling clean blows in a match where the styles never quite clicked, with frequent clinching marring the fight.
Two judges scored it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my greatest showing but what do champions do? They win," Buatsi stated in the ring as he was greeted with disapproval from the crowd.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers thought the challenger, thirty-one, deserved the victory but the contender endured the second setback of his 28-match career.
Buatsi Claims Triumph in Slow Match
The fighter's advancement has plateaued in the past few years through promotional disputes and long spells of lack of fights.
Earlier forecast as the future of the British fight scene, he now stands trying to achieve expectations - possibly in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with neither fighter prepared to take risks in a tentative opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second appearance at light heavyweight.
By the halfway stage, Parker had made it competitive, causing problems for Buatsi, who utilized a protective stance to barely take the more effective rounds.
The crowd's patience decreased because of frequent holding, with the challenger falling to the floor multiple occasions during clinches.
The underdog ended stronger, but many rounds were hard to judge. Although, ex-champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
The victor moves on, but with the likes of heavy hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Homage Inspires All-Manchester Contest
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a terrific all-Manchester contest to capture the European light heavyweight belt.
The arena fell silent for a profoundly moving memorial prior to the bout as a bell ceremony sounded in honor of the city's native Hatton, who died aged 46 in recently.
It was the premier televised fight night in the location since Hatton's death. As the concluding sound disappeared, the quiet gave way to a chant of "there's just one Hatton".
The competition inside the ropes matched the feeling. The eventual winner was floored by a significant blow flush on the face in the second round, rising shakily to his position on the eight count.
But the traditional red attire of Arthur soon came forward again. On the opposite side, Rea - in opposing blue - was injured soon, heavy swelling forming under his orbital area as the pair exchanged hard punches.
The challenger, 27, connected with strong blows but Arthur, thirty-four, responded in kind with stinging uppercuts as the pace seldom decreased over the full distance.
The victor barely secured the verdict with scoring tallies of even score, narrow lead and 115-112, but the two athletes were relentless and full of heart, all the qualities their inspiration the legend embodied.
