UK light heavyweight Joshua Buatsi earned a win yet disappointing beginning to life under recent management with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a competitive ten-round fight at the boxing arena.
But the challenger landed significant shots, delivering effective clean blows in a match where the approaches didn't complement each other, with frequent clinching marring the action.
The scoring judges had it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They win," the victor said in the ringside as he was greeted with negative reactions from the spectators.
The British fighter returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in last winter - to secure a 20th pro success.
Several boxing experts felt the challenger, thirty-one, should have been awarded the decision but the contender experienced the second setback of his 28-bout career.
Buatsi Claims Triumph in Slow Affair
His career development has plateaued in the past few years through contract problems and extended periods of lack of fights.
Once tipped as the future of UK boxing, he now finds himself trying to fulfil that early promise - perhaps in what appears to be a last chance - under fresh management.
He started carefully, with both competitors prepared to take risks in a tentative opening few rounds.
Parker, whose only previous defeat came at super-middleweight against his former opponent in two years ago after breaking his hand mid-fight, was making just his second fight at light-heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for Buatsi, who worked behind a protective stance to narrowly win the better stanzas.
The spectators' acceptance wore thin because of frequent holding, with Parker slipping to the canvas several times during clinches.
Parker ended stronger, but multiple periods were difficult to score. However, ex-champion the boxing analyst - working with the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just only one stanza.
The victor advances, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Hatton Tribute Motivates Local Rivalry Fight
In the secondary fight, Arthur defeated Bradley Rea by divided decision in a outstanding local rivalry battle to win the continental belt.
The venue fell silent for a deeply poignant homage before the fight as 10 bells tolled in memory 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 the passing of Hatton. As the concluding sound disappeared, the quiet became a shout of "there's only one Hatton".
The competition during the bout reflected the sentiment. Arthur was knocked down by a left hook flush on the jaw in the second round, standing uncertainly to his footing on the count of eight.
But the Manchester United-red equipment of the fighter soon came forward again. From the other corner, the opponent - in rival City blue - was injured soon, heavy swelling appearing under his orbital area as the duo landed punishing blows.
Rea, twenty-seven, connected with strong blows but the champion, 34, fought fire with fire with powerful upward punches as the intensity seldom decreased over the full distance.
The victor edged the decision with scoring tallies of even score, 115-113 and wider gap, but each competitor were persistent and brave, exactly what their idol the legend stood for.
