British light-heavyweight Joshua Buatsi earned a win yet unimpressive debut to life under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a split decision in a tight 10-round contest at the boxing arena.
But Parker had his moments, landing some telling single shots in a match where the techniques failed to mesh, with constant grabbing marring the action.
The officials scored it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my finest performance but what defines champions? They succeed," Buatsi said in the ring as he was faced negative reactions from the crowd.
The British fighter bounced back after his maiden career setback - an epic battle with his previous opponent in last winter - to earn a 20th career victory.
Several boxing experts thought Parker, thirty-one, merited the victory but the British boxer endured the second setback of his 28-match career.
The Champion Earns Triumph in Dull Match
Buatsi's progress has slowed in recent times through promotional disputes and extended periods of inactivity.
Once tipped as the next star of UK boxing, he now finds himself trying to realize his potential - perhaps in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter willing to overcommit in a tentative opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in two years ago after suffering a hand injury in the contest, was making just his second bout at light-heavyweight.
By the halfway stage, Parker had stayed in contention, making life awkward for the favorite, who utilized a tight guard to edge the better periods.
The crowd's patience decreased during frequent holding, with Parker slipping to the canvas multiple occasions during grappling.
The underdog finished the stronger, but many rounds were challenging to assess. Although, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi progresses, but with the presence of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Homage Inspires Local Rivalry Battle
In the supporting bout, Arthur defeated Rea by split-decision in a outstanding all-Manchester contest to win the continental belt.
The stadium fell silent for a profoundly moving memorial ahead of the contest as ten bells rang in memory of Manchester's own Ricky Hatton, who passed away 46 years old in recently.
It was the premier televised fight night in the location since the passing of Hatton. As the concluding sound disappeared, the silence transitioned to a shout of "only one Ricky Hatton".
The fighting inside the ropes reflected the sentiment. Arthur was sent to the canvas by a significant blow squarely on the jaw in the early round, getting up unsteadily to his position on the referee's count.
But the red-colored equipment of the fighter soon came forward again. From the other corner, Rea - in opposing blue - was marked up early, noticeable damage forming under his eye as the fighters landed punishing blows.
The challenger, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the pace rarely dropped over 12 rounds.
Arthur barely secured the verdict with scoring tallies of even score, narrow lead and 115-112, but each competitor were relentless and courageous, exactly what their idol Hatton represented.
