British light-heavyweight Buatsi earned a win yet underwhelming beginning to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a judges' verdict in a tight 10-round fight at the boxing arena.
But the challenger landed significant shots, landing some telling single shots in a contest where the techniques didn't complement each other, with constant grabbing disrupting the action.
The officials had it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my finest display but what do champions do? They succeed," Buatsi said in the ringside as he was met by boos from the crowd.
The British fighter got back to winning after his maiden career setback - an memorable fight with his previous opponent in last winter - to earn a 20th career victory.
Some ringside observers felt Parker, thirty-one, merited the win but the contender endured the second loss of his 28-match career.
Buatsi Secures Win in Dull Encounter
The fighter's advancement has stalled in recent times through management issues and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now stands trying to realize his potential - maybe in what appears to be a last chance - under fresh management.
He began cautiously, with both competitors prepared to overcommit in a calculated opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in 2022 after suffering a hand injury mid-fight, was participating in his second appearance at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for the favorite, who utilized a solid defense to barely take the better periods.
The spectators' acceptance diminished during regular grabbing, with Parker slipping to the canvas several times during grappling.
The underdog closed well, but several stanzas were challenging to assess. Nevertheless, former world champion Carl Frampton - working with the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just a single round.
Buatsi advances, but with the likes of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Homage Inspires Manchester Derby Contest
In the co-main event, Arthur defeated Rea by close verdict in a excellent local rivalry fight to secure the European light heavyweight championship.
The venue grew hushed for a extremely emotional tribute prior to the bout as a bell ceremony tolled in honor of Manchester's own Hatton, who died aged 46 in recently.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the final chime ended, the silence gave way to a shout of "only one Hatton".
The action during the bout equaled the emotion. Arthur was floored by a powerful punch squarely on the chin in the initial stage, rising shakily to his feet on the referee's count.
But the traditional red equipment of Arthur soon pressed ahead again. From the other corner, the opponent - in competitive blue - was damaged early, significant bruising appearing under his eye as the fighters landed powerful shots.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace rarely dropped over twelve rounds.
The victor barely secured the result with official scores of draw, 115-113 and wider gap, but the two athletes were determined and full of heart, exactly what their inspiration Hatton stood for.
