UK light heavyweight Joshua Buatsi made a winning yet disappointing beginning to his career under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a majority decision in a competitive 10-round fight at the boxing arena.
But the challenger had his moments, connecting with powerful single shots in a contest where the styles failed to mesh, with constant grabbing spoiling the contest.
The officials had it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest display but what defines champions? They succeed," the victor commented in the arena as he was faced disapproval from the audience.
The Londoner returned to winning ways after his maiden career setback - an epic battle with his previous opponent in February - to claim a 20th career victory.
Several boxing experts thought Parker, 31, should have been awarded the decision but the Derbyshire fighter experienced the second setback of his 28-match professional journey.
The Champion Secures Win in Slow Affair
Buatsi's progress has stalled in recent years through promotional disputes and long spells of inactivity.
Previously predicted as the rising talent of UK boxing, he now finds himself trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter ready to be aggressive in a tentative early stages.
Parker, whose sole prior loss came at super middleweight against John Ryder in two years ago after breaking his hand during the bout, was making just his second appearance at light heavyweight.
By the halfway stage, the underdog had made it competitive, making life awkward for the favorite, who utilized a solid defense to narrowly win the cleaner periods.
The audience's tolerance decreased amid constant clinching, with the challenger going down multiple occasions during clinches.
Parker closed well, but many rounds were difficult to score. Nevertheless, former world champion the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, giving Buatsi just one round.
Buatsi progresses, but with the presence of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Memorial Inspires Manchester Derby Contest
In the secondary fight, Arthur defeated Bradley Rea by split-decision in a outstanding local rivalry fight to capture the European light-heavyweight belt.
The arena fell silent for a extremely emotional homage ahead of the contest as ten bells rang in memory of local hero Hatton, who passed away at age 46 in September.
It was the premier televised fight night in the city since the passing of Hatton. As the last bell disappeared, the silence became a shout of "there's only one Hatton".
The fighting within the ring reflected the emotion. Arthur was sent to the canvas by a powerful punch squarely on the chin in the early round, getting up unsteadily to his footing on the count of eight.
But the Manchester United-red shorts of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was damaged quickly, noticeable damage forming under his eye as the pair landed punishing blows.
Rea, 27, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the action hardly diminished over twelve rounds.
Arthur narrowly won the result with judges scorecards of 114-114, 115-113 and wider gap, but both fighters were relentless and courageous, exactly what their idol the legend embodied.
