British light heavyweight Buatsi made a winning yet unimpressive start to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a tight ten-round fight at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling clean blows in a match where the styles never quite clicked, with constant grabbing marring the action.
The scoring judges judged it 96-94 for to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They prevail," the victor stated in the arena as he was faced negative reactions 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 secure a 20th pro success.
Various analysts believed the challenger, thirty-one, deserved the decision but the British boxer endured the second setback of his 28-fight professional journey.
The Champion Claims Victory in Dull Affair
Buatsi's progress has stalled in recent times through promotional disputes and considerable time of inactivity.
Earlier forecast as the future of UK boxing, he now stands trying to achieve expectations - maybe in what appears to be a final roll of the dice - under recent support.
He started carefully, with neither fighter ready to be aggressive in a cagey opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was making just his second appearance at light heavyweight.
By the halfway stage, Parker had made it competitive, making life awkward for Buatsi, who worked behind a tight guard to edge the cleaner rounds.
The crowd's patience wore thin because of constant clinching, with the challenger falling to the floor several times during clinches.
The underdog ended stronger, but several stanzas were hard to judge. However, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, giving Buatsi just a single round.
The victor progresses, but with the likes of power puncher Benavidez, and Russian star Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Tribute Inspires Manchester Derby Fight
In the supporting bout, Lyndon Arthur beat Bradley Rea by split-decision in a terrific all-Manchester fight to capture the European light heavyweight belt.
The venue grew hushed for a extremely emotional tribute prior to the bout as ten bells rang in memory of local hero Ricky Hatton, who died 46 years old in September.
It was the first major televised boxing event in the urban center since the passing of Hatton. As the last bell ended, the stillness gave way to a shout of "there's only one Hatton".
The fighting within the ring reflected the emotion. The eventual winner was knocked down by a significant blow flush on the jaw in the initial stage, standing uncertainly to his position on the eight count.
But the traditional red shorts of the fighter soon came forward again. From the other corner, the opponent - in rival City blue - was damaged early, noticeable damage appearing under his eye as the fighters exchanged hard punches.
Rea, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the intensity rarely dropped over 12 rounds.
Arthur narrowly won the verdict with scoring tallies of 114-114, close margin and wider gap, but each competitor were relentless and brave, exactly what their hero the legend embodied.
