British light-heavyweight Joshua Buatsi earned a win yet underwhelming start to his career under recent management with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a tight ten-round fight at the Co-op Live Arena.
But Parker had his moments, connecting with powerful single shots in a match where the approaches didn't complement each other, with frequent clinching spoiling the contest.
The scoring judges had it 96-94 for to the winner, with the third a even score.
"It wasn't my best performance but what defines champions? They win," Buatsi stated in the ringside as he was met by negative reactions from the crowd.
The Londoner got back to winning after his first professional defeat - an thrilling contest with his previous opponent in last winter - to secure a 20th career victory.
Some ringside observers thought the challenger, thirty-one, merited the victory but the contender suffered the second loss of his 28-match career.
The Champion Earns Win in Slow Affair
His career development has slowed in recent years through management issues and extended periods of inactivity.
Previously predicted as the next star of the British fight scene, he now is positioned trying to fulfil that early promise - perhaps in what appears to be a ultimate opportunity - under recent support.
He opened tentatively, with the two boxers willing to overcommit in a tentative early stages.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand mid-fight, was participating in his second bout at light heavyweight.
By the halfway stage, Parker had kept it close, causing problems for the favorite, who operated with a solid defense to edge the better rounds.
The spectators' acceptance decreased during regular grabbing, with the challenger going down multiple occasions during grappling.
The underdog ended stronger, but several stanzas were difficult to score. Although, ex-champion the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
The victor progresses, but with the caliber of hard hitter David Benavidez, and Russian champion Bivol ruling the division, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Memorial Motivates Local Rivalry Contest
In the supporting bout, Arthur beat Bradley Rea by divided decision in a terrific all-Manchester battle to capture the European light-heavyweight championship.
The arena became quiet for a extremely emotional memorial ahead of the contest as 10 bells rang in honor of local hero Ricky Hatton, who passed away 46 years old in recently.
It was the premier televised match card in the urban center since the passing of Hatton. As the last bell disappeared, the stillness became a chant of "only one Ricky Hatton".
The fighting during the bout matched the emotion. Arthur was sent to the canvas by a powerful punch flush on the chin in the initial stage, rising shakily to his feet on the referee's count.
But the traditional red shorts of the fighter soon advanced again. From the other corner, Rea - in competitive blue - was injured quickly, significant bruising appearing under his eye as the pair landed punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, responded in kind with stinging uppercuts as the pace hardly diminished over 12 rounds.
The victor barely secured the result with official scores of 114-114, narrow lead and clearer margin, but each competitor were persistent and brave, everything their idol Hatton represented.
