British light heavyweight Joshua Buatsi secured a victory yet disappointing debut to life under new promoters with a unanimous decision over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a tight ten-round bout at the Manchester venue.
But the challenger found success, delivering effective individual punches in a fight where the techniques didn't complement each other, with constant grabbing spoiling the fight.
The scoring judges judged it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest display but how do champions respond? They prevail," Buatsi commented in the ringside as he was met by disapproval from the crowd.
The British fighter bounced back after his initial pro loss - an thrilling contest with Callum Smith in February - to secure a 20th career victory.
Some ringside observers thought the challenger, 31, should have been awarded the decision but the contender suffered the second loss of his 28-fight career.
The Champion Secures Victory in Dull Affair
The fighter's advancement has plateaued in the past few years through promotional disputes and extended periods of inactivity.
Previously predicted as the next star of UK boxing, he now stands trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with both competitors ready to take risks in a calculated initial rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after damaging his hand mid-fight, was participating in his second appearance at the higher weight class.
By the halfway stage, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a tight guard to edge the cleaner rounds.
The spectators' acceptance diminished because of regular grabbing, with the challenger going down several times during clinches.
The underdog ended stronger, but multiple periods were challenging to assess. However, ex-champion Carl Frampton - working with Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the caliber of power puncher Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Homage Fuels All-Manchester Battle
In the supporting bout, Arthur beat Rea by divided decision in a terrific Manchester vs Manchester battle to secure the European light heavyweight belt.
The arena became quiet for a extremely emotional memorial before the fight as a bell ceremony tolled in honor of the city's native Hatton, who died at age 46 in recently.
It was the first major televised boxing event in the urban center since Hatton's passing. As the concluding sound ended, the silence became a roar of "only one Ricky Hatton".
The fighting during the bout equaled the sentiment. The eventual winner was sent to the canvas by a powerful punch squarely on the jaw in the initial stage, standing uncertainly to his footing on the count of eight.
But the Manchester United-red equipment of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was injured early, noticeable damage developing under his orbital area as the fighters exchanged powerful shots.
Rea, 27, connected with strong blows but the champion, thirty-four, matched the intensity with effective uppercuts as the pace rarely dropped over twelve rounds.
Arthur edged the result with official scores of draw, 115-113 and 115-112, but both fighters were persistent and full of heart, exactly what their hero the legend embodied.
