British light heavyweight Buatsi earned a win yet unimpressive debut to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a majority decision in a tight 10-round contest at the boxing arena.
But the challenger landed significant shots, landing some telling clean blows in a contest where the styles never quite clicked, with frequent clinching spoiling the fight.
The scoring judges scored it 96-94 to Buatsi, with the final judge a even score.
"It wasn't my finest display but what defines champions? They succeed," Buatsi said in the ring as he was greeted with disapproval from the spectators.
The Londoner returned to winning ways after his first professional defeat - an epic battle with Callum Smith in February - to earn a 20th career victory.
Various analysts felt the challenger, thirty-one, merited the victory but the contender suffered the second setback of his 28-bout career.
Buatsi Earns Triumph in Uneventful Encounter
Buatsi's progress has stalled in the past few years through management issues and extended periods of lack of fights.
Once tipped as the next star of British boxing, he now finds himself trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with the two boxers prepared to take risks in a cagey early stages.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was making just his second bout at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for Buatsi, who operated with a solid defense to narrowly win the better periods.
The spectators' acceptance wore thin because of constant clinching, with Parker going down various instances during clinches.
The underdog closed well, but several stanzas were difficult to score. However, ex-champion the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just one round.
The victor moves on, but with the likes of heavy hitter Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Tribute Inspires All-Manchester Battle
In the co-main event, Arthur beat Rea by split-decision in a outstanding local rivalry fight to win the continental title.
The stadium became quiet for a profoundly moving memorial before the fight as 10 bells tolled in honor of the city's native Hatton, who passed away aged 46 in recently.
It was the premier televised fight night in the city since Hatton's passing. As the final chime disappeared, the quiet became a chant of "only one Hatton".
The competition during the bout reflected the sentiment. The eventual winner was knocked down by a powerful punch squarely on the face in the second round, standing uncertainly to his feet on the count of eight.
But the traditional red shorts of Arthur soon came forward again. Across the ring, Rea - in opposing blue - was damaged early, noticeable damage appearing under his eye as the fighters exchanged powerful shots.
Rea, 27, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the action rarely dropped over the full distance.
The victor edged the decision with scoring tallies of even score, close margin and 115-112, but the two athletes were determined and brave, all the qualities their inspiration Hatton embodied.
