British light-heavyweight Buatsi earned a win yet underwhelming start to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a split decision in a competitive ten-round contest at the Manchester venue.
But the challenger landed significant shots, connecting with powerful individual punches in a fight where the styles didn't complement each other, with frequent clinching marring the contest.
Two judges scored it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest performance but what do champions do? They succeed," the victor commented in the arena as he was greeted with disapproval from the crowd.
The British fighter bounced back after his maiden career setback - an memorable fight with his previous opponent in last winter - to secure a twentieth professional win.
Various analysts felt the challenger, thirty-one, merited the victory but the Derbyshire fighter endured the second defeat of his 28-fight professional journey.
The Champion Secures Win in Dull Affair
The fighter's advancement has plateaued in recent years through management issues and considerable time of inactivity.
Previously predicted as the rising talent of UK boxing, he now is positioned trying to achieve expectations - perhaps in what seems like a last chance - under new promotional backing.
He began cautiously, with neither fighter ready to overcommit in a calculated initial rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after damaging his hand in the contest, was competing in only his second appearance at light heavyweight.
By the middle rounds, the underdog had made it competitive, creating difficulties for the favorite, who operated with a solid defense to barely take the more effective rounds.
The audience's tolerance wore thin because of constant clinching, with Parker falling to the floor various instances during grappling.
The underdog ended stronger, but several stanzas were challenging to assess. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just only one stanza.
The victor moves on, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still looks steep.
Hatton Tribute Inspires All-Manchester Battle
In the co-main event, Arthur defeated Rea by split-decision in a excellent Manchester vs Manchester contest to secure the European light heavyweight belt.
The arena grew hushed for a deeply poignant memorial prior to the bout as ten bells tolled in memory of the city's native Hatton, who passed away at age 46 in last month.
It was the premier televised boxing event in the location since the passing of Hatton. As the concluding sound disappeared, the quiet transitioned to a shout of "only one Ricky Hatton".
The competition inside the ropes matched the emotion. Arthur was knocked down by a powerful punch flush on the face in the initial stage, getting up unsteadily to his footing on the referee's count.
But the Manchester United-red shorts of Arthur soon came forward again. Across the ring, the opponent - in rival City blue - was injured early, noticeable damage forming under his orbital area as the fighters traded punishing blows.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with powerful upward punches as the action rarely dropped over twelve rounds.
Arthur barely secured the decision with judges scorecards of even score, narrow lead and 115-112, but both fighters were relentless and brave, everything their idol Hatton embodied.
