UK light-heavyweight Buatsi made a winning yet underwhelming start to his career under recent management with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a competitive 10-round fight at the Manchester venue.
But the challenger had his moments, landing some telling individual punches in a fight where the techniques didn't complement each other, with excessive holding spoiling the fight.
The officials scored it 96-94 in favor to the winner, with the third a even score.
"It wasn't my finest display but what do champions do? They prevail," the victor said in the ring as he was faced negative reactions from the audience.
The British fighter bounced back after his maiden career setback - an memorable fight with Callum Smith in February - to secure a 20th career victory.
Several boxing experts believed the challenger, thirty-one, deserved the decision but the British boxer experienced the second defeat of his 28-match professional journey.
The Champion Claims Win in Slow Affair
Buatsi's progress has slowed in the past few years through contract problems and long spells of inactivity.
Previously predicted as the rising talent of the British fight scene, he now is positioned trying to fulfil that early promise - perhaps in what feels like a final roll of the dice - under fresh management.
He started carefully, with both competitors prepared to take risks in a cagey initial rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was making just his second fight at light heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for Buatsi, who operated with a tight guard to narrowly win the better rounds.
The audience's tolerance wore thin amid frequent holding, with Parker falling to the floor several times during grappling.
The underdog closed well, but several stanzas were hard to judge. Nevertheless, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, awarding Buatsi just a single round.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Hatton Homage Inspires Local Rivalry Contest
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a outstanding local rivalry fight to win the European light-heavyweight belt.
The arena grew hushed for a deeply poignant memorial before the fight as ten bells rang in honor of Manchester's own Hatton, who passed away aged 46 in last month.
It was the first major televised fight night in the urban center since the passing of Hatton. As the concluding sound disappeared, the quiet became a shout of "only one Ricky Hatton".
The competition within the ring matched the sentiment. The eventual winner was sent to the canvas by a significant blow squarely on the jaw in the initial stage, rising shakily to his feet on the count of eight.
But the traditional red equipment of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was marked up soon, noticeable damage forming under his orbital area as the duo landed powerful shots.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with powerful upward punches as the intensity hardly diminished over twelve rounds.
The victor narrowly won the result with judges scorecards of even score, close margin and 115-112, but each competitor were determined and brave, exactly what their hero Hatton represented.
