British light-heavyweight Joshua Buatsi made a winning yet underwhelming start to his career under new promoters with a unanimous decision over Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a majority decision in a tight ten-round contest at the Manchester venue.
But the challenger had his moments, landing some telling clean blows in a fight where the techniques failed to mesh, with constant grabbing disrupting the contest.
The scoring judges judged it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my finest performance but what do champions do? They prevail," Buatsi commented in the arena as he was greeted with negative reactions from the spectators.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in February - to claim a twentieth professional win.
Various analysts felt Parker, 31, should have been awarded the victory but the British boxer suffered the second defeat of his 28-bout professional journey.
The Champion Claims Triumph in Uneventful Match
The fighter's advancement has stalled in the past few years through management issues and considerable time of lack of fights.
Previously predicted as the next star of British boxing, he now stands trying to realize his potential - maybe in what feels like a last chance - under fresh management.
He opened tentatively, with both competitors ready to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in 2022 after damaging his hand mid-fight, was competing in only his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for the favorite, who worked behind a protective stance to narrowly win the more effective periods.
The crowd's patience diminished because of regular grabbing, with Parker slipping to the canvas several times during grappling.
Parker finished the stronger, but many rounds were challenging to assess. Nevertheless, ex-champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just one round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates All-Manchester Contest
In the co-main event, Lyndon Arthur defeated Rea by close verdict in a excellent Manchester vs Manchester fight to secure the European light heavyweight championship.
The arena grew hushed for a extremely emotional homage prior to the bout as ten bells sounded in honor of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the initial significant broadcast fight night in the city since Hatton's death. As the final chime ended, the quiet gave way to a shout of "there's just one Hatton".
The competition during the bout matched the emotion. The eventual winner was knocked down by a left hook directly to the chin in the second round, getting up unsteadily to his feet on the eight count.
But the traditional red shorts of Arthur soon came forward again. From the other corner, Rea - in rival City blue - was marked up early, significant bruising forming under his face as the duo landed hard punches.
Rea, 27, connected with strong blows but the champion, 34, responded in kind with powerful upward punches as the intensity seldom decreased over the full distance.
The victor barely secured the result with scoring tallies of 114-114, 115-113 and clearer margin, but each competitor were relentless and full of heart, everything their idol Hatton represented.
