British light-heavyweight Joshua Buatsi made a winning yet unimpressive start to his career under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a competitive ten-round fight at the Manchester venue.
But the challenger had his moments, landing some telling individual punches in a fight where the styles didn't complement each other, with frequent clinching disrupting the fight.
The scoring judges scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest performance but how do champions respond? They win," the victor stated in the arena as he was faced boos from the audience.
The Londoner bounced back after his initial pro loss - an memorable fight with his previous opponent in last winter - to earn a 20th career victory.
Various analysts felt Parker, 31, deserved the win but the British boxer endured the second setback of his 28-bout career.
The Champion Claims Win in Dull Encounter
His career development has slowed in recent years through promotional disputes and long spells of inactivity.
Once tipped as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with both competitors willing to be aggressive in a calculated opening few rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second appearance at light-heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for the favorite, who worked behind a protective stance to barely take the better periods.
The crowd's patience wore thin during frequent holding, with Parker slipping to the canvas several times during close exchanges.
Parker finished the stronger, but several stanzas were difficult to score. Although, ex-champion Carl Frampton - commentating on the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the presence of hard hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Homage Inspires Local Rivalry Fight
In the secondary fight, Arthur defeated Rea by divided decision in a terrific local rivalry fight to secure the European light-heavyweight championship.
The arena grew hushed for a extremely emotional memorial prior to the bout as 10 bells rang in remembrance of the city's native Ricky Hatton, who passed away 46 years old in recently.
It was the premier televised fight night in the urban center since Hatton's death. As the concluding sound faded, the silence transitioned to a chant of "only one Hatton".
The fighting inside the ropes matched the sentiment. Arthur was floored by a left hook flush on the chin in the second round, getting up unsteadily to his position on the referee's count.
But the red-colored equipment of the fighter soon pressed ahead again. Across the ring, the opponent - in competitive blue - was marked up quickly, heavy swelling developing under his orbital area as the duo traded hard punches.
The challenger, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with powerful upward punches as the intensity rarely dropped over twelve rounds.
Arthur barely secured the verdict with judges scorecards of 114-114, narrow lead and 115-112, but the two athletes were determined and brave, everything their inspiration Hatton embodied.
