British light heavyweight Joshua Buatsi earned a win yet underwhelming start to life under new promoters with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a competitive ten-round bout at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling single shots in a fight where the techniques failed to mesh, with excessive holding spoiling the fight.
Two judges had it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my best showing but how do champions respond? They prevail," the victor said in the ringside as he was faced negative reactions from the crowd.
The British fighter returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in February - to claim a twentieth professional win.
Various analysts believed Parker, 31, deserved the win but the Derbyshire fighter experienced the second defeat of his 28-fight professional journey.
The Champion Secures Win in Dull Match
Buatsi's progress has plateaued in recent years through management issues and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now stands trying to fulfil that early promise - perhaps in what appears to be a last chance - under fresh management.
He opened tentatively, with both competitors ready to overcommit in a calculated early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after damaging his hand mid-fight, was making just his second bout at the higher weight class.
By the middle rounds, Parker had kept it close, causing problems for the favorite, who utilized a protective stance to edge the cleaner rounds.
The audience's tolerance diminished because of regular grabbing, with the challenger going down various instances during clinches.
Parker finished the stronger, but several stanzas were hard to judge. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, giving Buatsi just one round.
The victor moves on, but with the caliber of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Hatton Memorial Fuels Manchester Derby Contest
In the co-main event, Arthur overcame Bradley Rea by split-decision in a terrific local rivalry battle to capture the European light-heavyweight belt.
The stadium became quiet for a deeply poignant homage prior to the bout as 10 bells rang in memory of Manchester's own Ricky Hatton, who succumbed aged 46 in September.
It was the premier televised fight night in the urban center since Hatton's death. As the final chime faded, the silence transitioned to a shout of "there's only one Ricky Hatton".
The fighting within the ring reflected the emotion. Arthur was floored by a left hook flush on the jaw in the second round, getting up unsteadily to his footing on the referee's count.
But the red-colored shorts of the fighter soon came forward again. Across the ring, Rea - in rival City blue - was damaged quickly, noticeable damage appearing under his orbital area as the duo exchanged hard punches.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with stinging uppercuts as the pace seldom decreased over the full distance.
The victor edged the verdict with judges scorecards of draw, close margin and wider gap, but the two athletes were relentless and full of heart, everything their idol the legend stood for.
