British light-heavyweight Joshua Buatsi made a winning yet disappointing start to his career under recent management with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a majority decision in a competitive 10-round contest at the Co-op Live Arena.
But Parker had his moments, delivering effective single shots in a contest where the approaches failed to mesh, with constant grabbing spoiling the action.
The officials had it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They prevail," the victor commented in the ringside as he was faced negative reactions from the spectators.
The Londoner got back to winning after his initial pro loss - an thrilling contest with Callum Smith in February - to claim a 20th career victory.
Some ringside observers believed Parker, 31, merited the victory but the Derbyshire fighter endured the second setback of his 28-bout career.
Buatsi Claims Win in Uneventful Affair
Buatsi's progress has plateaued in recent years through contract problems and considerable time of lack of fights.
Earlier forecast as the future of UK boxing, he now is positioned trying to realize his potential - perhaps in what feels like a last chance - under fresh management.
He began cautiously, with both competitors prepared to be aggressive in a calculated opening few rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after damaging his hand in the contest, was competing in only his second fight at light-heavyweight.
By the middle rounds, Parker had made it competitive, causing problems for the favorite, who worked behind a solid defense to barely take the better rounds.
The crowd's patience wore thin during frequent holding, with Parker falling to the floor several times during close exchanges.
Parker ended stronger, but several stanzas were difficult to score. However, ex-champion the boxing analyst - working with Dazn - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
The victor advances, but with the caliber of power puncher Benavidez, and Eastern European fighter Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Hatton Homage Motivates Local Rivalry Battle
In the supporting bout, Arthur overcame Rea by divided decision in a outstanding Manchester vs Manchester battle to secure the European light heavyweight belt.
The stadium fell silent for a profoundly moving tribute ahead of the contest as ten bells rang in honor of local hero Hatton, who passed away aged 46 in recently.
It was the premier televised match card in the location since Hatton's passing. As the concluding sound faded, the stillness became a chant of "there's only one Hatton".
The action inside the ropes matched the sentiment. Arthur was knocked down by a significant blow squarely on the face in the early round, standing uncertainly to his footing on the eight count.
But the Manchester United-red equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in opposing blue - was marked up soon, noticeable damage developing under his orbital area as the duo landed punishing blows.
Rea, 27, delivered effective strikes but the champion, 34, fought fire with fire with powerful upward punches as the action hardly diminished over twelve rounds.
Arthur edged the decision with scoring tallies of even score, narrow lead and clearer margin, but each competitor were determined and brave, everything their hero the legend stood for.
