UK light heavyweight Buatsi secured a victory yet disappointing beginning to life under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a competitive 10-round contest at the Manchester venue.
But the challenger found success, landing some telling individual punches in a contest where the styles didn't complement each other, with excessive holding spoiling the action.
Two judges scored it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my greatest performance but how do champions respond? They prevail," the victor commented in the ring as he was faced negative reactions from the crowd.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts believed Parker, thirty-one, deserved the win but the contender endured the second setback of his 28-fight career.
Buatsi Secures Victory in Slow Affair
The fighter's advancement has stalled in recent times through promotional disputes and considerable time of lack of fights.
Earlier forecast as the rising talent of UK boxing, he now stands trying to fulfil that early promise - maybe in what seems like a last chance - under fresh management.
He opened tentatively, with both competitors prepared to overcommit in a calculated opening few rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand in the contest, was making just his second bout at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, making life awkward for Buatsi, who worked behind a solid defense to barely take the better periods.
The crowd's patience decreased because of regular grabbing, with Parker falling to the floor several times during grappling.
The underdog ended stronger, but many rounds were hard to judge. Nevertheless, former world champion the boxing analyst - providing analysis for Dazn - had it significantly in favor for Parker, giving Buatsi just only one stanza.
The victor advances, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Memorial Motivates Local Rivalry Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a outstanding local rivalry fight to secure the European light heavyweight belt.
The stadium fell silent for a deeply poignant tribute prior to the bout as 10 bells sounded in honor of local hero Hatton, who passed away aged 46 in last month.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the concluding sound disappeared, the silence gave way to a roar of "there's just one Ricky Hatton".
The action inside the ropes matched the sentiment. The eventual winner was floored by a significant blow directly to the face in the second round, rising shakily to his position on the referee's count.
But the traditional red shorts of Arthur soon came forward again. Across the ring, the opponent - in rival City blue - was damaged quickly, heavy swelling forming under his orbital area as the pair traded powerful shots.
Rea, 27, connected with strong blows but Arthur, thirty-four, fought fire with fire with effective uppercuts as the intensity hardly diminished over the full distance.
Arthur edged the verdict with scoring tallies of draw, 115-113 and clearer margin, but the two athletes were determined and courageous, all the qualities their inspiration the legend stood for.
