British light heavyweight Joshua Buatsi secured a victory yet disappointing debut to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a tight ten-round contest at the boxing arena.
But the challenger had his moments, landing some telling single shots in a contest where the styles failed to mesh, with constant grabbing spoiling the action.
The scoring judges scored it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest performance but what defines champions? They succeed," Buatsi commented in the ring as he was greeted with disapproval from the audience.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in last winter - to secure a 20th career victory.
Several boxing experts believed the challenger, thirty-one, deserved the victory but the contender suffered the second loss of his 28-bout professional journey.
The Champion Claims Win in Uneventful Affair
His career development has stalled in the past few years through promotional disputes and extended periods of inactivity.
Previously predicted as the next star of UK boxing, he now is positioned trying to realize his potential - possibly in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with both competitors willing to overcommit in a cagey opening few rounds.
Parker, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, creating difficulties for Buatsi, who utilized a tight guard to narrowly win the cleaner stanzas.
The crowd's patience diminished during constant clinching, with the challenger falling to the floor multiple occasions during close exchanges.
The underdog finished the stronger, but multiple periods were hard to judge. Nevertheless, previous titleholder the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi advances, but with the caliber of hard hitter David Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Hatton Tribute Fuels All-Manchester Contest
In the supporting bout, Lyndon Arthur defeated Bradley Rea by split-decision in a excellent all-Manchester battle to win the continental belt.
The arena grew hushed for a profoundly moving tribute ahead of the contest as a bell ceremony sounded in remembrance of the city's native Ricky Hatton, who passed away 46 years old in last month.
It was the premier televised fight night in the city since the passing of Hatton. As the last bell ended, the quiet gave way to a chant of "there's only one Hatton".
The action during the bout matched the sentiment. The eventual winner was floored by a powerful punch flush on the jaw in the initial stage, rising shakily to his position on the referee's count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. From the other corner, Rea - in rival City blue - was damaged early, noticeable damage appearing under his eye as the duo exchanged powerful shots.
The challenger, 27, delivered effective strikes but Arthur, 34, responded in kind with powerful upward punches as the intensity hardly diminished over the full distance.
The victor edged the result with scoring tallies of even score, 115-113 and wider gap, but the two athletes were relentless and courageous, everything their inspiration the legend stood for.
