British light heavyweight Joshua Buatsi earned a win yet disappointing beginning to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a competitive ten-round contest at the Manchester venue.
But Parker had his moments, delivering effective individual punches in a fight where the approaches failed to mesh, with constant grabbing disrupting the fight.
The scoring judges scored it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my finest display but what defines champions? They succeed," Buatsi said in the arena as he was met by disapproval from the crowd.
The Londoner got back to winning after his initial pro loss - an thrilling contest with Callum Smith in last winter - to earn a twentieth professional win.
Several boxing experts felt the challenger, 31, should have been awarded the decision but the contender experienced the second setback of his 28-fight career.
Buatsi Earns Triumph in Uneventful Match
Buatsi's progress has stalled in recent times through promotional disputes and extended periods of lack of fights.
Previously predicted as the rising talent of British boxing, he now is positioned trying to realize his potential - perhaps in what seems like a final roll of the dice - under fresh management.
He started carefully, with the two boxers ready to be aggressive in a cagey early stages.
Parker, whose single earlier setback came at super middleweight against his former opponent in 2022 after breaking his hand in the contest, was competing in only his second appearance at light-heavyweight.
By the middle rounds, Parker had stayed in contention, causing problems for the favorite, who worked behind a tight guard to edge the cleaner rounds.
The crowd's patience wore thin amid frequent holding, with Parker falling to the floor several times during close exchanges.
The underdog ended stronger, but many rounds were difficult to score. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
The victor advances, but with the likes of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still looks steep.
Hatton Memorial Inspires Manchester Derby Fight
In the secondary fight, Lyndon Arthur beat Rea by split-decision in a outstanding local rivalry fight to secure the European light heavyweight belt.
The arena became quiet for a extremely emotional homage before the fight as ten bells tolled in memory of Manchester's own Ricky Hatton, who succumbed 46 years old in September.
It was the first major televised boxing event in the urban center since Hatton's passing. As the concluding sound ended, the stillness gave way to a chant of "there's only one Hatton".
The action during the bout reflected the sentiment. The eventual winner was knocked down by a significant blow squarely on the face in the second round, standing uncertainly to his footing on the eight count.
But the red-colored attire of Arthur soon advanced again. On the opposite side, Rea - in rival City blue - was marked up early, heavy swelling developing under his eye as the duo landed powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, matched the intensity with stinging uppercuts as the action rarely dropped over 12 rounds.
The victor edged the decision with scoring tallies of even score, narrow lead and wider gap, but both fighters were determined and courageous, all the qualities their inspiration Hatton embodied.
