British light heavyweight Joshua Buatsi secured a victory yet disappointing debut to life under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a tight 10-round fight at the Manchester venue.
But Parker had his moments, connecting with powerful clean blows in a contest where the techniques failed to mesh, with frequent clinching marring the action.
Two judges judged it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my best showing but how do champions respond? They prevail," the victor stated in the arena as he was greeted with boos from the audience.
The British fighter got back to winning after his maiden career setback - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers believed the challenger, thirty-one, deserved the decision but the British boxer endured the second defeat of his 28-match career.
Buatsi Secures Victory in Slow Encounter
Buatsi's progress has plateaued in recent times through contract problems and long spells of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now stands trying to realize his potential - maybe in what appears to be a ultimate opportunity - under recent support.
He started carefully, with both competitors ready to take risks in a cagey opening few rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was participating in his second fight at light-heavyweight.
By the halfway stage, Parker had kept it close, making life awkward for Buatsi, who operated with a tight guard to narrowly win the better stanzas.
The crowd's patience wore thin amid frequent holding, with Parker slipping to the canvas several times during close exchanges.
Parker ended stronger, but many rounds were difficult to score. However, ex-champion the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, giving Buatsi just one round.
The victor advances, but with the presence of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Hatton Homage Motivates Manchester Derby Battle
In the co-main event, Lyndon Arthur beat Rea by close verdict in a excellent all-Manchester battle to secure the continental belt.
The arena fell silent for a extremely emotional tribute prior to the bout as 10 bells tolled in memory of Manchester's own Hatton, who passed away at age 46 in last month.
It was the premier televised match card in the urban center since the passing of Hatton. As the concluding sound ended, the silence gave way to a chant of "there's just one Ricky Hatton".
The fighting during the bout equaled the sentiment. The eventual winner was sent to the canvas by a left hook directly to the face in the initial stage, standing uncertainly to his footing on the count of eight.
But the red-colored shorts of Arthur soon came forward again. On the opposite side, the opponent - in opposing blue - was injured soon, heavy swelling developing under his eye as the fighters exchanged hard punches.
The challenger, twenty-seven, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the action hardly diminished over 12 rounds.
Arthur edged the decision with official scores of 114-114, narrow lead and wider gap, but the two athletes were persistent and full of heart, exactly what their hero Hatton represented.
