British light-heavyweight Joshua Buatsi earned a win yet underwhelming start to life under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a close 10-round fight at the boxing arena.
But Parker landed significant shots, landing some telling individual punches in a fight where the approaches never quite clicked, with frequent clinching marring the contest.
The scoring judges scored it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my best performance but what do champions do? They succeed," Buatsi commented in the ring as he was faced disapproval from the audience.
The British fighter returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in February - to claim a 20th career victory.
Several boxing experts thought Parker, 31, should have been awarded the victory but the contender suffered the second defeat of his 28-match professional journey.
Buatsi Secures Victory in Uneventful Encounter
His career development has slowed in recent times through management issues and considerable time of lack of fights.
Earlier forecast as the future of the British fight scene, he now stands trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with the two boxers prepared to overcommit in a calculated initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after damaging his hand mid-fight, was competing in only his second bout at light heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for the favorite, who worked behind a protective stance to barely take the better rounds.
The crowd's patience decreased because of frequent holding, with Parker going down various instances during clinches.
The underdog ended stronger, but many rounds were difficult to score. However, former world champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for Parker, giving Buatsi just a single round.
The victor moves on, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Tribute Motivates Local Rivalry Contest
In the secondary fight, Lyndon Arthur beat Bradley Rea by split-decision in a terrific all-Manchester contest to win the continental belt.
The arena grew hushed for a extremely emotional tribute before the fight as 10 bells sounded in remembrance of local hero Ricky Hatton, who succumbed 46 years old in recently.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the concluding sound disappeared, the stillness gave way to a roar of "there's just one Hatton".
The competition within the ring equaled the feeling. The eventual winner was knocked down by a significant blow directly to the jaw in the second round, getting up unsteadily to his feet on the referee's count.
But the traditional red shorts of Arthur soon pressed ahead again. Across the ring, Rea - in rival City blue - was damaged quickly, heavy swelling appearing under his eye as the duo exchanged powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, 34, matched the intensity with stinging uppercuts as the pace hardly diminished over twelve rounds.
Arthur narrowly won the result with official scores of draw, narrow lead and wider gap, but each competitor were persistent and full of heart, exactly what their hero the legend stood for.
