UK light heavyweight Buatsi earned a win yet unimpressive beginning to life under recent management with a points victory over Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a split decision in a competitive 10-round bout at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful individual punches in a contest where the styles never quite clicked, with excessive holding disrupting the action.
The officials judged it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my greatest showing but what do champions do? They prevail," the victor said in the ringside as he was met by negative reactions from the spectators.
The British fighter got back to winning after his maiden career setback - an thrilling contest with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts felt Parker, 31, deserved the win but the British boxer endured the second setback of his 28-match professional journey.
The Champion Secures Victory in Dull Affair
Buatsi's progress has slowed in the past few years through promotional disputes and considerable time of lack of fights.
Once tipped as the future of British boxing, he now finds himself trying to realize his potential - maybe in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with the two boxers ready to overcommit in a cagey early stages.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, 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 operated with a protective stance to narrowly win the cleaner rounds.
The crowd's patience diminished because of constant clinching, with Parker going down various instances during grappling.
Parker closed well, but many rounds were hard to judge. Although, previous titleholder the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just one round.
Buatsi progresses, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - on this evidence - still appears challenging.
Hatton Tribute Inspires Local Rivalry Battle
In the co-main event, Arthur defeated Bradley Rea by split-decision in a terrific Manchester vs Manchester contest to secure the continental championship.
The arena fell silent for a profoundly moving tribute ahead of the contest as a bell ceremony rang in memory of the city's native Ricky Hatton, who succumbed aged 46 in last month.
It was the premier televised fight night in the location since the passing of Hatton. As the last bell ended, the silence became a shout of "there's just one Hatton".
The fighting inside the ropes equaled the sentiment. The eventual winner was floored by a significant blow squarely on the jaw in the initial stage, standing uncertainly to his position on the count of eight.
But the traditional red shorts of Arthur soon came forward again. On the opposite side, the opponent - in opposing blue - was damaged soon, heavy swelling forming under his orbital area as the fighters exchanged powerful shots.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, responded in kind with effective uppercuts as the pace seldom decreased over twelve rounds.
Arthur edged the verdict with scoring tallies of 114-114, narrow lead and wider gap, but each competitor were relentless and brave, exactly what their idol the legend represented.
