British light-heavyweight Buatsi made a winning yet disappointing start to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a split decision in a close 10-round bout at the Manchester venue.
But the challenger had his moments, delivering effective single shots in a contest where the approaches never quite clicked, with constant grabbing disrupting the contest.
The scoring judges scored it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my best display but how do champions respond? They succeed," Buatsi stated in the ringside as he was greeted with negative reactions from the spectators.
The British fighter got back to winning after his initial pro loss - an epic battle with Callum Smith in last winter - to secure a 20th career victory.
Various analysts thought Parker, thirty-one, should have been awarded the victory but the British boxer experienced the second loss of his 28-match professional journey.
The Champion Claims Victory in Dull Affair
His career development has stalled in recent years through promotional disputes and long spells of inactivity.
Earlier forecast as the future of UK boxing, he now stands trying to realize his potential - maybe in what appears to be a ultimate opportunity - under recent support.
He opened tentatively, with neither fighter ready to take risks in a calculated early stages.
The challenger, whose single earlier setback came at super middleweight against his former opponent in 2022 after damaging his hand in the contest, was competing in only his second appearance at light-heavyweight.
By the middle rounds, the underdog had stayed in contention, making life awkward for the favorite, who operated with a tight guard to barely take the cleaner rounds.
The crowd's patience decreased because of frequent holding, with the challenger falling to the floor multiple occasions during clinches.
The underdog closed well, but several stanzas were challenging to assess. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just a single round.
Buatsi moves on, but with the presence of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - judging by this showing - still seems difficult.
Hatton Memorial Motivates Manchester Derby Contest
In the supporting bout, Lyndon Arthur overcame Bradley Rea by split-decision in a excellent all-Manchester fight to secure the continental belt.
The venue grew hushed for a deeply poignant homage prior to the bout as a bell ceremony sounded in remembrance of the city's native Hatton, who succumbed at age 46 in last month.
It was the first major televised match card in the city since Hatton's passing. As the concluding sound faded, the stillness became a roar of "only one Ricky Hatton".
The competition during the bout matched the feeling. Arthur was sent to the canvas by a powerful punch flush on the chin in the second round, getting up unsteadily to his feet on the referee's count.
But the red-colored attire of the fighter soon came forward again. From the other corner, the opponent - in competitive blue - was injured quickly, heavy swelling appearing under his orbital area as the fighters exchanged powerful shots.
Rea, twenty-seven, landed power punches but Arthur, 34, responded in kind with effective uppercuts as the pace hardly diminished over twelve rounds.
The victor narrowly won the verdict with official scores of 114-114, 115-113 and 115-112, but each competitor were determined and brave, everything their hero the legend represented.
