British light-heavyweight Joshua Buatsi made a winning yet unimpressive start to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a competitive ten-round bout at the boxing arena.
But Parker had his moments, connecting with powerful single shots in a match where the techniques never quite clicked, with constant grabbing disrupting the contest.
The scoring judges scored it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my best showing but what defines champions? They succeed," Buatsi stated in the ring as he was faced negative reactions from the spectators.
The Londoner bounced back after his initial pro loss - an memorable fight with his previous opponent in last winter - to earn a 20th career victory.
Several boxing experts thought the challenger, 31, deserved the victory but the Derbyshire fighter experienced the second setback of his 28-bout career.
The Champion Earns Triumph in Slow Match
His career development has plateaued in the past few years through contract problems and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now stands trying to fulfil that early promise - maybe in what seems like a final roll of the dice - under new promotional backing.
He started carefully, with neither fighter prepared to overcommit in a tentative opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after suffering a hand injury mid-fight, was participating in his second bout at light heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for Buatsi, who utilized a protective stance to edge the better periods.
The spectators' acceptance wore thin amid regular grabbing, with Parker slipping to the canvas several times during grappling.
The underdog closed well, but several stanzas were hard to judge. However, ex-champion the boxing analyst - commentating on Dazn - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Hatton Homage Fuels Manchester Derby Battle
In the co-main event, Lyndon Arthur beat Rea by divided decision in a outstanding all-Manchester fight to capture the continental championship.
The arena fell silent for a deeply poignant memorial prior to the bout as a bell ceremony rang in remembrance of Manchester's own Hatton, who passed away 46 years old in recently.
It was the premier televised boxing event in the location since Hatton's passing. As the concluding sound faded, the quiet gave way to a shout of "there's just one Hatton".
The action within the ring matched the feeling. The eventual winner was sent to the canvas by a left hook directly to the jaw in the second round, standing uncertainly to his footing on the eight count.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was injured quickly, significant bruising appearing under his eye as the pair exchanged powerful shots.
The challenger, 27, delivered effective strikes but Arthur, 34, responded in kind with effective uppercuts as the action rarely dropped over 12 rounds.
The victor narrowly won the result with official scores of even score, narrow lead and wider gap, but the two athletes were relentless and full of heart, exactly what their hero the legend stood for.
