British light-heavyweight Buatsi secured a victory yet unimpressive start to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a judges' verdict in a competitive ten-round contest at the boxing arena.
But the challenger landed significant shots, landing some telling individual punches in a fight where the techniques failed to mesh, with constant grabbing marring the fight.
The officials scored it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my best display but how do champions respond? They win," the victor stated in the arena as he was faced negative reactions from the audience.
The Londoner bounced back after his first professional defeat - an memorable fight with Callum Smith in last winter - to secure a 20th career victory.
Some ringside observers felt Parker, thirty-one, merited the victory but the British boxer endured the second setback of his 28-bout career.
The Champion Earns Victory in Dull Affair
His career development has slowed in recent times through contract problems and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now stands trying to realize his potential - perhaps in what appears to be a ultimate opportunity - under recent support.
He opened tentatively, with both competitors prepared to take risks in a cagey opening few rounds.
Parker, whose sole prior loss came at super-middleweight against his former opponent in 2022 after breaking his hand mid-fight, was making just his second appearance at light heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for Buatsi, who utilized a solid defense to barely take the better rounds.
The crowd's patience wore thin amid frequent holding, with the challenger falling to the floor several times during clinches.
The underdog ended stronger, but multiple periods were hard to judge. However, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just one round.
The victor moves on, but with the caliber of heavy hitter David Benavidez, and Russian champion Bivol ruling the division, the road to world glory - judging by this showing - still looks steep.
Hatton Homage Motivates Manchester Derby Contest
In the co-main event, Arthur defeated Rea by close verdict in a terrific local rivalry fight to capture the European light-heavyweight championship.
The stadium became quiet for a extremely emotional tribute before the fight as ten bells tolled in remembrance of Manchester's own Hatton, who succumbed 46 years old in September.
It was the initial significant broadcast fight night in the city since Hatton's death. As the last bell faded, the silence transitioned to a shout of "only one Hatton".
The competition during the bout matched the feeling. The eventual winner was sent to the canvas by a significant blow flush on the chin in the initial stage, getting up unsteadily to his footing on the eight count.
But the traditional red attire of Arthur soon came forward again. On the opposite side, Rea - in rival City blue - was damaged soon, noticeable damage appearing under his orbital area as the duo landed punishing blows.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur barely secured the result with scoring tallies of 114-114, narrow lead and clearer margin, but both fighters were determined and brave, everything their idol Hatton stood for.
