UK light heavyweight Buatsi earned a win yet unimpressive beginning to his career under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a tight ten-round bout at the boxing arena.
But the challenger landed significant shots, delivering effective single shots in a contest where the techniques never quite clicked, with constant grabbing marring the contest.
The officials had it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my finest performance but what defines champions? They win," the victor said in the arena as he was faced disapproval from the crowd.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers believed Parker, thirty-one, deserved the victory but the contender endured the second defeat of his 28-fight professional journey.
The Champion Claims Win in Uneventful Match
The fighter's advancement has plateaued in recent times through contract problems and extended periods of lack of fights.
Once tipped as the rising talent of British boxing, he now is positioned trying to realize his potential - maybe in what feels like a ultimate opportunity - under recent support.
He began cautiously, with the two boxers prepared to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in 2022 after breaking his hand mid-fight, was making just his second bout at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, making life awkward for the favorite, who utilized a solid defense to barely take the better stanzas.
The crowd's patience decreased amid constant clinching, with Parker falling to the floor various instances during close exchanges.
Parker closed well, but many rounds were difficult to score. Although, former world champion Carl Frampton - working with the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
Buatsi progresses, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates All-Manchester Fight
In the co-main event, Arthur beat Rea by divided decision in a excellent local rivalry fight to capture the continental belt.
The arena grew hushed for a profoundly moving memorial before the fight as 10 bells sounded in memory of Manchester's own Ricky Hatton, who succumbed at age 46 in recently.
It was the initial significant broadcast fight night in the city since Hatton's death. As the concluding sound ended, the silence gave way to a shout of "only one Ricky Hatton".
The action within the ring equaled the feeling. The eventual winner was floored by a significant blow squarely on the chin in the initial stage, rising shakily to his position on the count of eight.
But the traditional red shorts of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was marked up quickly, heavy swelling forming under his orbital area as the duo traded powerful shots.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with effective uppercuts as the intensity seldom decreased over 12 rounds.
Arthur edged the verdict with official scores of 114-114, 115-113 and 115-112, but each competitor were determined and brave, all the qualities their hero the legend represented.
