British light heavyweight Joshua Buatsi secured a victory yet underwhelming start to life under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a tight ten-round fight at the Manchester venue.
But the challenger had his moments, connecting with powerful clean blows in a fight where the styles failed to mesh, with excessive holding marring the fight.
The officials scored it 96-94 to the winner, with the remaining official a even score.
"It wasn't my best display but how do champions respond? They win," Buatsi said in the ring as he was faced disapproval from the spectators.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to claim a twentieth professional win.
Some ringside observers believed Parker, 31, merited the decision but the Derbyshire fighter suffered the second loss of his 28-match career.
The Champion Claims Triumph in Uneventful Affair
His career development has slowed in recent times through contract problems and extended periods of inactivity.
Earlier forecast as the future of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what appears to be a final roll of the dice - under recent support.
He started carefully, with neither fighter prepared to take risks in a cagey initial rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in two years ago after breaking his hand during the bout, was making just his second fight at light heavyweight.
By the halfway stage, the underdog had kept it close, creating difficulties for Buatsi, who utilized a tight guard to barely take the more effective rounds.
The audience's tolerance decreased amid frequent holding, with Parker going down various instances during close exchanges.
Parker finished the stronger, but many rounds were difficult to score. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just one round.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Russian star Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Hatton Tribute Inspires Manchester Derby Fight
In the co-main event, Lyndon Arthur beat Bradley Rea by close verdict in a terrific local rivalry battle to win the European light heavyweight championship.
The arena became quiet for a extremely emotional tribute ahead of the contest as ten bells tolled in remembrance of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the first major televised fight night in the location since the passing of Hatton. As the final chime faded, the silence gave way to a chant of "there's only one Ricky Hatton".
The action within the ring matched the emotion. Arthur was sent to the canvas by a powerful punch flush on the jaw in the initial stage, rising shakily to his position on the referee's count.
But the red-colored attire of Arthur soon pressed ahead again. From the other corner, Rea - in opposing blue - was damaged quickly, significant bruising appearing under his face as the duo landed punishing blows.
Rea, 27, delivered effective strikes but the champion, 34, responded in kind with stinging uppercuts as the intensity seldom decreased over the full distance.
Arthur narrowly won the decision with judges scorecards of draw, 115-113 and wider gap, but each competitor were relentless and courageous, everything their inspiration the legend embodied.
