UK light heavyweight Buatsi earned a win yet unimpressive start to life under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a competitive 10-round contest at the boxing arena.
But the challenger landed significant shots, connecting with powerful single shots in a fight where the approaches failed to mesh, with constant grabbing marring the contest.
The scoring judges judged it 96-94 in favor to the winner, with the third a even score.
"It wasn't my finest performance but what do champions do? They prevail," Buatsi stated in the arena as he was met by negative reactions from the audience.
The British fighter returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in February - to earn a twentieth professional win.
Some ringside observers thought the challenger, 31, should have been awarded the victory but the British boxer suffered the second loss of his 28-fight professional journey.
Buatsi Secures Victory in Uneventful Encounter
Buatsi's progress has slowed in recent years through management issues and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now is positioned trying to realize his potential - perhaps in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors prepared to take risks in a cagey early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was participating in his second appearance at light heavyweight.
By the fight's midpoint, Parker had kept it close, causing problems for Buatsi, who operated with a tight guard to barely take the cleaner rounds.
The spectators' acceptance diminished during regular grabbing, with the challenger falling to the floor several times during close exchanges.
The underdog ended stronger, but several stanzas were challenging to assess. Nevertheless, ex-champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just only one stanza.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - based on this performance - still seems difficult.
Hatton Tribute Motivates Manchester Derby Battle
In the supporting bout, Lyndon Arthur beat Bradley Rea by split-decision in a outstanding local rivalry contest to win the European light heavyweight belt.
The stadium grew hushed for a extremely emotional homage ahead of the contest as a bell ceremony tolled in remembrance of Manchester's own Hatton, who died at age 46 in last month.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the last bell disappeared, the stillness transitioned to a shout of "only one Hatton".
The fighting during the bout matched the emotion. The eventual winner was floored by a powerful punch directly to the face in the initial stage, rising shakily to his feet on the referee's count.
But the Manchester United-red shorts of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was damaged soon, heavy swelling developing under his face as the duo exchanged powerful shots.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with stinging uppercuts as the intensity hardly diminished over twelve rounds.
Arthur edged the result with official scores of 114-114, narrow lead and 115-112, but each competitor were persistent and courageous, everything their inspiration Hatton represented.
