British light-heavyweight Joshua Buatsi earned a win yet underwhelming beginning to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a tight ten-round bout at the boxing arena.
But the challenger had his moments, connecting with powerful individual punches in a fight where the approaches didn't complement each other, with constant grabbing spoiling the contest.
Two judges judged it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my finest performance but what do champions do? They win," the victor said in the ring as he was greeted with disapproval from the audience.
The British fighter got back to winning after his initial pro loss - an epic battle with Callum Smith in last winter - to secure a twentieth professional win.
Various analysts felt Parker, 31, merited the victory but the Derbyshire fighter experienced the second setback of his 28-fight professional journey.
The Champion Earns Victory in Dull Match
The fighter's advancement has slowed in recent times through contract problems and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to realize his potential - possibly in what appears to be a ultimate opportunity - under new promotional backing.
He started carefully, with both competitors ready to overcommit in a calculated opening few rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was participating in his second fight at light-heavyweight.
By the halfway stage, Parker had made it competitive, making life awkward for the favorite, who utilized a tight guard to narrowly win the cleaner rounds.
The crowd's patience diminished amid frequent holding, with Parker falling to the floor various instances during grappling.
The underdog closed well, but several stanzas were challenging to assess. However, ex-champion Carl Frampton - working with the broadcast network - had it strongly leaning for Parker, awarding Buatsi just one round.
Buatsi advances, but with the likes of heavy hitter Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Memorial Inspires All-Manchester Battle
In the supporting bout, Arthur overcame Bradley Rea by divided decision in a excellent Manchester vs Manchester contest to capture the European light heavyweight title.
The venue grew hushed for a profoundly moving memorial ahead of the contest as a bell ceremony sounded in memory of the city's native Ricky Hatton, who died at age 46 in last month.
It was the premier televised match card in the location since Hatton's passing. As the last bell ended, the silence gave way to a shout of "there's only one Hatton".
The fighting inside the ropes matched the emotion. The eventual winner was knocked down by a left hook squarely on the face in the early round, getting up unsteadily to his footing on the eight count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. Across the ring, Rea - in opposing blue - was marked up quickly, noticeable damage forming under his orbital area as the fighters traded powerful shots.
Rea, 27, connected with strong blows but Arthur, thirty-four, responded in kind with stinging uppercuts as the pace rarely dropped over 12 rounds.
Arthur barely secured the verdict with scoring tallies of draw, 115-113 and wider gap, but each competitor were determined and full of heart, exactly what their inspiration the legend represented.
