UK light heavyweight Buatsi earned a win yet unimpressive debut to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a close 10-round fight at the boxing arena.
But the challenger found success, connecting with powerful clean blows in a contest where the techniques didn't complement each other, with constant grabbing disrupting the action.
The scoring judges judged it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my finest showing but what defines champions? They prevail," Buatsi commented in the arena as he was faced negative reactions from the audience.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in February - to earn a twentieth professional win.
Various analysts felt the challenger, thirty-one, should have been awarded the victory but the contender experienced the second defeat of his 28-bout career.
Buatsi Secures Win in Dull Affair
Buatsi's progress has stalled in the past few years through contract problems and long spells of lack of fights.
Previously predicted as the rising talent of UK boxing, he now finds himself trying to realize his potential - perhaps in what seems like a last chance - under new promotional backing.
He started carefully, with neither fighter willing to overcommit in a cagey opening few rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was making just his second bout at the higher weight class.
By the halfway stage, the underdog had made it competitive, causing problems for the favorite, who operated with a solid defense to barely take the more effective rounds.
The spectators' acceptance wore thin because of constant clinching, with Parker slipping to the canvas several times during close exchanges.
Parker closed well, but many rounds were difficult to score. Nevertheless, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, giving Buatsi just a single round.
Buatsi moves on, but with the presence of hard hitter David Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - on this evidence - still looks steep.
Hatton Memorial Inspires Local Rivalry Battle
In the co-main event, Arthur beat Bradley Rea by split-decision in a terrific local rivalry fight to win the European light heavyweight belt.
The stadium grew hushed for a profoundly moving memorial ahead of the contest as ten bells rang in memory of the city's native Hatton, who died 46 years old in last month.
It was the initial significant broadcast fight night in the city since Hatton's passing. As the final chime disappeared, the quiet became a chant of "only one Hatton".
The action within the ring reflected the feeling. Arthur was sent to the canvas by a significant blow squarely on the jaw in the second round, getting up unsteadily to his position on the referee's count.
But the traditional red equipment of the fighter soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up soon, noticeable damage developing under his orbital area as the fighters exchanged punishing blows.
Rea, 27, delivered effective strikes but Arthur, 34, fought fire with fire with stinging uppercuts as the pace rarely dropped over 12 rounds.
The victor narrowly won the verdict with official scores of even score, close margin and 115-112, but both fighters were relentless and courageous, all the qualities their inspiration Hatton embodied.
