British light-heavyweight Buatsi secured a victory yet disappointing start to his career under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a tight 10-round contest at the Co-op Live Arena.
But the challenger had his moments, delivering effective clean blows in a contest where the techniques failed to mesh, with frequent clinching disrupting the action.
The officials scored it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest showing but how do champions respond? They succeed," the victor stated in the arena as he was greeted with boos from the crowd.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in February - to claim a 20th pro success.
Various analysts thought the challenger, thirty-one, merited the decision but the Derbyshire fighter suffered the second defeat of his 28-bout career.
Buatsi Claims Victory in Dull Encounter
The fighter's advancement has slowed in recent times through promotional disputes and considerable time of inactivity.
Once tipped as the future of British boxing, he now finds himself trying to realize his potential - perhaps in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with both competitors prepared to take risks in a cagey early stages.
Parker, whose sole prior loss came at the lower weight class 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 stayed in contention, causing problems for Buatsi, who operated with a tight guard to edge the more effective periods.
The audience's tolerance decreased during constant clinching, with the challenger slipping to the canvas various instances during grappling.
Parker closed well, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
Buatsi progresses, but with the likes of power puncher David Benavidez, and Russian star Bivol leading the category, the road to world glory - on this evidence - still seems difficult.
Hatton Tribute Fuels All-Manchester Fight
In the co-main event, Lyndon Arthur defeated Bradley Rea by split-decision in a excellent Manchester vs Manchester fight to capture the continental championship.
The venue became quiet for a deeply poignant memorial ahead of the contest as ten bells sounded in memory of local hero Hatton, who passed away at age 46 in last month.
It was the premier televised match card in the urban center since the passing of Hatton. As the final chime disappeared, the quiet became a shout of "there's only one Ricky Hatton".
The fighting inside the ropes equaled the sentiment. Arthur was sent to the canvas by a left hook flush on the chin in the initial stage, standing uncertainly to his feet on the referee's count.
But the red-colored equipment of Arthur soon came forward again. From the other corner, the opponent - in rival City blue - was damaged early, noticeable damage forming under his orbital area as the pair traded punishing blows.
Rea, twenty-seven, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the pace rarely dropped over 12 rounds.
The victor edged the verdict with scoring tallies of draw, narrow lead and wider gap, but the two athletes were relentless and brave, exactly what their idol the legend stood for.
