British light heavyweight Joshua Buatsi made a winning yet disappointing debut to life under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a competitive ten-round contest at the Manchester venue.
But the challenger found success, landing some telling individual punches in a contest where the styles didn't complement each other, with excessive holding spoiling the action.
Two judges judged it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my greatest showing but what do champions do? They win," Buatsi commented in the ringside as he was faced disapproval from the crowd.
The Londoner bounced back after his first professional defeat - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts felt the challenger, 31, deserved the win but the Derbyshire fighter suffered the second loss of his 28-fight professional journey.
The Champion Earns Victory in Slow Encounter
His career development has stalled in recent years through management issues and long spells of inactivity.
Once tipped as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what seems like a last chance - under fresh management.
He opened tentatively, with both competitors willing to take risks in a calculated initial rounds.
Parker, whose single earlier setback came at the lower weight class against his former opponent in two years ago after damaging his hand in the contest, was competing in only his second fight at light heavyweight.
By the halfway stage, Parker had kept it close, making life awkward for the favorite, who worked behind a tight guard to narrowly win the better rounds.
The spectators' acceptance wore thin amid frequent holding, with the challenger going down various instances during grappling.
The underdog ended stronger, but multiple periods were difficult to score. However, ex-champion Carl Frampton - commentating on Dazn - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
The victor moves on, but with the caliber of power puncher Benavidez, and Russian champion Bivol leading the category, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Memorial Motivates Local Rivalry Battle
In the co-main event, Arthur overcame Bradley Rea by split-decision in a terrific all-Manchester contest to capture the European light heavyweight belt.
The arena grew hushed for a profoundly moving memorial ahead of the contest as 10 bells rang in remembrance of local hero Ricky Hatton, who passed away 46 years old in September.
It was the first major televised boxing event in the city since Hatton's passing. As the last bell ended, the silence became a roar of "only one Ricky Hatton".
The competition during the bout reflected the sentiment. Arthur was sent to the canvas by a left hook squarely on the chin in the second round, rising shakily to his feet on the count of eight.
But the Manchester United-red shorts of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was injured quickly, noticeable damage forming under his face as the duo traded hard punches.
Rea, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the pace rarely dropped over 12 rounds.
The victor edged the decision with scoring tallies of draw, close margin and wider gap, but both fighters were persistent and courageous, everything their inspiration the legend represented.
