British light-heavyweight Joshua Buatsi made a winning yet disappointing debut to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a split decision in a competitive 10-round contest at the Co-op Live Arena.
But the challenger found success, delivering effective individual punches in a fight where the approaches failed to mesh, with excessive holding disrupting the fight.
The scoring judges judged it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest performance but what do champions do? They prevail," the victor stated in the ringside as he was faced boos from the audience.
The Londoner got back to winning after his maiden career setback - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Several boxing experts felt Parker, thirty-one, should have been awarded the decision but the Derbyshire fighter suffered the second setback of his 28-match career.
Buatsi Earns Victory in Dull Match
Buatsi's progress has slowed in the past few years through contract problems and long spells of inactivity.
Previously predicted as the next star of British boxing, he now finds himself trying to achieve expectations - possibly in what appears to be a last chance - under recent support.
He started carefully, with both competitors ready to overcommit in a calculated early stages.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after suffering a hand injury mid-fight, was participating in his second fight at light-heavyweight.
By the halfway stage, Parker had made it competitive, making life awkward for the favorite, who utilized a solid defense to narrowly win the better periods.
The spectators' acceptance wore thin amid constant clinching, with Parker slipping to the canvas multiple occasions during clinches.
The underdog ended stronger, but several stanzas were challenging to assess. Although, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, giving Buatsi just one round.
Buatsi moves on, but with the caliber of power puncher Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - based on this performance - still seems difficult.
Hatton Tribute Motivates Manchester Derby Battle
In the secondary fight, Lyndon Arthur defeated Bradley Rea by divided decision in a excellent all-Manchester contest to secure the European light heavyweight championship.
The arena became quiet for a profoundly moving memorial prior to the bout as 10 bells tolled in remembrance of the city's native Hatton, who passed away at age 46 in last month.
It was the premier televised fight night in the city since the passing of Hatton. As the last bell faded, the silence became a shout of "there's only one Hatton".
The competition within the ring reflected the feeling. The eventual winner was knocked down by a significant blow flush on the jaw in the early round, standing uncertainly to his feet on the count of eight.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was injured early, noticeable damage developing under his face as the pair traded punishing blows.
The challenger, twenty-seven, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur barely secured the decision with official scores of 114-114, close margin and wider gap, but the two athletes were determined and courageous, exactly what their hero the legend represented.
