UK light-heavyweight Joshua Buatsi secured a victory yet disappointing start to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a majority decision in a competitive ten-round fight at the Manchester venue.
But Parker landed significant shots, delivering effective single shots in a fight where the styles didn't complement each other, with constant grabbing disrupting the action.
The officials scored it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest performance but how do champions respond? They succeed," the victor stated in the ring as he was met by boos from the crowd.
The British fighter bounced back after his maiden career setback - an epic battle with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts thought Parker, thirty-one, should have been awarded the victory but the contender endured the second setback of his 28-bout career.
The Champion Secures Triumph in Slow Encounter
Buatsi's progress has plateaued in recent years through promotional disputes and considerable time of lack of fights.
Earlier forecast as the next star of British boxing, he now is positioned trying to achieve expectations - possibly in what appears to be a last chance - under fresh management.
He opened tentatively, with both competitors willing to be aggressive in a calculated 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 making just his second fight at light-heavyweight.
By the fight's midpoint, Parker had kept it close, creating difficulties for the favorite, who utilized a protective stance to barely take the better stanzas.
The spectators' acceptance decreased during constant clinching, with Parker going down various instances during grappling.
The underdog finished the stronger, but many rounds were challenging to assess. However, ex-champion the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi progresses, but with the likes of heavy hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Hatton Homage Inspires All-Manchester Battle
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a terrific Manchester vs Manchester fight to secure the European light-heavyweight title.
The venue fell silent for a extremely emotional tribute before the fight as ten bells sounded in memory of the city's native Hatton, who passed away aged 46 in recently.
It was the first major televised match card in the urban center since Hatton's passing. As the last bell disappeared, the stillness gave way to a shout of "there's only one Ricky Hatton".
The action inside the ropes matched the emotion. The eventual winner was knocked down by a powerful punch directly to the chin in the second round, standing uncertainly to his feet on the referee's count.
But the Manchester United-red attire of the fighter soon came forward again. Across the ring, Rea - in competitive blue - was damaged early, significant bruising developing under his orbital area as the fighters landed powerful shots.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the pace hardly diminished over twelve rounds.
Arthur edged the result with judges scorecards of even score, narrow lead and wider gap, but both fighters were persistent and full of heart, everything their idol Hatton stood for.
