British light heavyweight Joshua Buatsi made a winning yet disappointing debut to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a close ten-round contest at the boxing arena.
But the challenger had his moments, landing some telling individual punches in a contest where the approaches failed to mesh, with constant grabbing spoiling the contest.
The scoring judges had it 96-94 to the winner, with the third a even score.
"It wasn't my finest performance but what do champions do? They win," the victor commented in the arena as he was faced negative reactions from the audience.
The British fighter returned to winning ways after his initial pro loss - an epic battle with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts believed the challenger, 31, should have been awarded the win but the Derbyshire fighter suffered the second defeat of his 28-match career.
Buatsi Claims Win in Dull Affair
The fighter's advancement has plateaued in the past few years through contract problems and considerable time of inactivity.
Previously predicted as the rising talent of UK boxing, he now finds himself trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with both competitors willing to overcommit in a cagey initial rounds.
Parker, 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 competing in only his second fight at light heavyweight.
By the fight's midpoint, the underdog had kept it close, making life awkward for the favorite, who worked behind a solid defense to narrowly win the more effective stanzas.
The crowd's patience diminished during regular grabbing, with the challenger going down several times during grappling.
Parker closed well, but several stanzas were hard to judge. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it significantly in favor for Parker, awarding Buatsi just a single round.
Buatsi moves on, but with the likes of power puncher Benavidez, and Russian star Bivol ruling the division, the road to world glory - on this evidence - still appears challenging.
Hatton Tribute Motivates Manchester Derby Fight
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a excellent local rivalry fight to win the European light heavyweight title.
The venue fell silent for a profoundly moving memorial before the fight as ten bells rang in memory of local hero Hatton, who died at age 46 in last month.
It was the initial significant broadcast fight night in the location since Hatton's death. As the last bell disappeared, the quiet gave way to a shout of "only one Hatton".
The competition during the bout reflected the feeling. Arthur was floored by a significant blow squarely on the jaw in the initial stage, standing uncertainly to his position on the eight count.
But the red-colored attire of Arthur soon came forward again. On the opposite side, Rea - in rival City blue - was marked up soon, noticeable damage forming under his eye as the pair exchanged powerful shots.
Rea, 27, connected with strong blows but Arthur, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over the full distance.
Arthur barely secured the verdict with official scores of draw, narrow lead and wider gap, but the two athletes were relentless and brave, all the qualities their hero Hatton embodied.
