British light heavyweight Buatsi secured a victory yet underwhelming debut to life under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a close ten-round contest at the Co-op Live Arena.
But the challenger found success, landing some telling clean blows in a match where the approaches never quite clicked, with constant grabbing disrupting the fight.
The officials judged it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest performance but how do champions respond? They prevail," Buatsi stated in the ringside as he was faced disapproval from the spectators.
The Londoner returned to winning ways after his maiden career setback - an epic battle with Callum Smith in last winter - to secure a 20th career victory.
Various analysts felt Parker, 31, should have been awarded the win but the Derbyshire fighter endured the second setback of his 28-bout professional journey.
The Champion Claims Triumph in Uneventful Affair
His career development has slowed in recent times through promotional disputes and considerable time of lack of fights.
Previously predicted as the future of the British fight scene, he now is positioned trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under recent support.
He began cautiously, with both competitors prepared to take risks in a tentative early stages.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for the favorite, who operated with a tight guard to narrowly win the more effective periods.
The spectators' acceptance wore thin during regular grabbing, with Parker falling to the floor multiple occasions during clinches.
The underdog ended stronger, but several stanzas were challenging to assess. Nevertheless, ex-champion the boxing analyst - commentating on Dazn - had it particularly wide for Parker, scoring for Buatsi just a single round.
Buatsi moves on, but with the presence of power puncher David Benavidez, and Russian champion Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Memorial Inspires Local Rivalry Contest
In the supporting bout, Lyndon Arthur overcame Bradley Rea by divided decision in a terrific all-Manchester battle to win the European light heavyweight belt.
The arena became quiet for a extremely emotional tribute prior to the bout as a bell ceremony sounded in remembrance of Manchester's own Hatton, who passed away aged 46 in last month.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the concluding sound disappeared, the silence became a shout of "there's only one Hatton".
The fighting inside the ropes reflected the feeling. Arthur was sent to the canvas by a left hook flush on the face in the early round, standing uncertainly to his position on the count of eight.
But the traditional red attire of the fighter soon advanced again. From the other corner, Rea - in competitive blue - was marked up soon, significant bruising developing under his orbital area as the fighters landed hard punches.
Rea, 27, landed power punches but the champion, 34, matched the intensity with stinging uppercuts as the action rarely dropped over the full distance.
The victor edged the result with scoring tallies of 114-114, close margin and wider gap, but each competitor were relentless and brave, exactly what their hero the legend stood for.
