British light-heavyweight Joshua Buatsi secured a victory yet underwhelming beginning to life under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a competitive ten-round fight at the Manchester venue.
But the challenger had his moments, landing some telling single shots in a contest where the styles never quite clicked, with frequent clinching marring the fight.
The officials had it 96-94 in favor to the winner, with the third a 95-95.
"It wasn't my finest showing but how do champions respond? They win," Buatsi commented in the ringside as he was met by boos from the audience.
The Londoner returned to winning ways after his first professional defeat - an epic battle with his previous opponent in last winter - to secure a twentieth professional win.
Various analysts believed Parker, thirty-one, deserved the win but the British boxer experienced the second loss of his 28-bout professional journey.
The Champion Secures Victory in Slow Encounter
The fighter's advancement has stalled in recent times through promotional disputes and considerable time of inactivity.
Once tipped as the rising talent of the British fight scene, he now is positioned trying to achieve expectations - possibly in what feels like a final roll of the dice - under fresh management.
He started carefully, with both competitors prepared to take risks in a cagey initial rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after damaging his hand in the contest, was participating in his second appearance at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who operated with a tight guard to edge the better rounds.
The spectators' acceptance diminished amid constant clinching, with the challenger falling to the floor multiple occasions during clinches.
The underdog ended stronger, but multiple periods were difficult to score. However, former world champion Carl Frampton - working with the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
Buatsi moves on, but with the presence of power puncher David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Tribute Motivates All-Manchester Contest
In the supporting bout, Lyndon Arthur defeated Bradley Rea by divided decision in a outstanding Manchester vs Manchester battle to capture the European light heavyweight championship.
The stadium became quiet for a profoundly moving tribute prior to the bout as a bell ceremony rang in remembrance of the city's native Ricky Hatton, who died at age 46 in last month.
It was the premier televised boxing event in the urban center since Hatton's death. As the concluding sound disappeared, the stillness became a shout of "only one Hatton".
The competition within the ring matched the feeling. Arthur was sent to the canvas by a significant blow flush on the chin in the initial stage, standing uncertainly to his position on the count of eight.
But the red-colored attire of Arthur soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was injured early, heavy swelling forming under his face as the duo landed hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, 34, fought fire with fire with effective uppercuts as the intensity hardly diminished over 12 rounds.
The victor barely secured the verdict with judges scorecards of even score, 115-113 and clearer margin, but both fighters were determined and full of heart, everything their hero the legend embodied.
