UK light-heavyweight Joshua Buatsi earned a win yet underwhelming start to life under new promoters with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a competitive ten-round contest at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling clean blows in a contest where the techniques failed to mesh, with constant grabbing marring the contest.
The officials had it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my best display but what defines champions? They succeed," the victor stated in the ring as he was met by negative reactions from the crowd.
The British fighter bounced back after his maiden career setback - an memorable fight with his previous opponent in last winter - to claim a twentieth professional win.
Several boxing experts felt Parker, 31, merited the win but the British boxer experienced the second setback of his 28-fight career.
Buatsi Secures Triumph in Dull Encounter
Buatsi's progress has plateaued in recent years through contract problems and long spells of inactivity.
Previously predicted as the future of UK boxing, he now is positioned trying to fulfil that early promise - perhaps in what appears to be a final roll of the dice - under new promotional backing.
He opened tentatively, with both competitors willing to take risks in a tentative opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after breaking his hand in the contest, was making just his second fight at light heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for the favorite, who worked behind a protective stance to edge the more effective rounds.
The crowd's patience decreased amid regular grabbing, with the challenger falling to the floor multiple occasions during clinches.
The underdog closed well, but many rounds were difficult to score. Nevertheless, previous titleholder Carl Frampton - working with Dazn - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the likes of power puncher Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - on this evidence - still seems difficult.
Hatton Homage Inspires All-Manchester Fight
In the supporting bout, Lyndon Arthur beat Bradley Rea by divided decision in a terrific Manchester vs Manchester fight to win the European light heavyweight belt.
The venue grew hushed for a extremely emotional memorial before the fight as ten bells rang in remembrance of the city's native Hatton, who died at age 46 in September.
It was the premier televised fight night in the urban center since Hatton's passing. As the concluding sound disappeared, the stillness transitioned to a shout of "there's only one Ricky Hatton".
The fighting during the bout equaled the feeling. The eventual winner was sent to the canvas by a powerful punch squarely on the chin in the early round, getting up unsteadily to his feet on the referee's count.
But the Manchester United-red attire of the fighter soon advanced again. From the other corner, the opponent - in rival City blue - was injured quickly, noticeable damage developing under his eye as the pair traded hard punches.
Rea, 27, connected with strong blows but Arthur, 34, matched the intensity with powerful upward punches as the action seldom decreased over 12 rounds.
The victor edged the result with judges scorecards of 114-114, close margin and clearer margin, but the two athletes were determined and brave, everything their inspiration Hatton embodied.
