UK light heavyweight Buatsi earned a win yet disappointing debut to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a close ten-round contest at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful clean blows in a contest where the approaches failed to mesh, with excessive holding spoiling the fight.
The scoring judges had it 96-94 for to the winner, with the remaining official a even score.
"It wasn't my finest display but how do champions respond? They win," the victor commented in the ring as he was faced boos from the crowd.
The Londoner bounced back after his maiden career setback - an memorable fight with his previous opponent in February - to claim a 20th career victory.
Several boxing experts believed the challenger, thirty-one, merited the win but the contender experienced the second setback of his 28-match professional journey.
Buatsi Claims Victory in Uneventful Match
His career development has plateaued in recent years through promotional disputes and considerable time of lack of fights.
Once tipped as the future of British boxing, he now is positioned trying to achieve expectations - maybe in what seems like a last chance - under new promotional backing.
He opened tentatively, with both competitors willing to overcommit in a cagey initial rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after suffering a hand injury during the bout, was competing in only his second appearance at light heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who operated with a protective stance to barely take the better rounds.
The crowd's patience decreased amid constant clinching, with the challenger falling to the floor various instances during close exchanges.
The underdog ended stronger, but several stanzas were hard to judge. However, ex-champion Carl Frampton - providing analysis for Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi progresses, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Tribute Fuels All-Manchester Battle
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a excellent local rivalry contest to capture the European light heavyweight title.
The venue grew hushed for a extremely emotional memorial prior to the bout as ten bells rang in honor of Manchester's own Hatton, who died 46 years old in September.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the concluding sound ended, the quiet transitioned to a chant of "there's only one Ricky Hatton".
The action during the bout equaled the sentiment. The eventual winner was sent to the canvas by a significant blow squarely on the chin in the initial stage, rising shakily to his position on the referee's count.
But the traditional red shorts of the fighter soon advanced again. On the opposite side, Rea - in opposing blue - was injured soon, noticeable damage forming under his orbital area as the pair exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, matched the intensity with powerful upward punches as the pace rarely dropped over 12 rounds.
The victor edged the verdict with official scores of even score, close margin and clearer margin, but both fighters were determined and brave, exactly what their inspiration Hatton represented.
