UK light heavyweight Joshua Buatsi secured a victory yet underwhelming debut to his career under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a competitive ten-round fight at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective single shots in a contest where the styles failed to mesh, with excessive holding spoiling the contest.
The scoring judges had it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my finest display but how do champions respond? They succeed," the victor commented in the ring as he was faced boos from the spectators.
The British fighter got back to winning after his first professional defeat - an thrilling contest with his previous opponent in last winter - to secure a twentieth professional win.
Some ringside observers thought the challenger, 31, merited the victory but the Derbyshire fighter suffered the second defeat of his 28-match professional journey.
Buatsi Secures Victory in Slow Encounter
His career development has slowed in recent years through promotional disputes and long spells of lack of fights.
Previously predicted as the future of the British fight scene, he now finds himself trying to realize his potential - perhaps in what feels like a last chance - under new promotional backing.
He opened tentatively, with both competitors willing to overcommit in a tentative initial rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second appearance at light-heavyweight.
By the middle rounds, Parker had stayed in contention, creating difficulties for Buatsi, who worked behind a protective stance to barely take the more effective periods.
The spectators' acceptance decreased because of frequent holding, with Parker falling to the floor multiple occasions during clinches.
The underdog closed well, but multiple periods were challenging to assess. Although, former world champion the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just one round.
The victor moves on, but with the likes of hard hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Memorial Motivates All-Manchester Fight
In the secondary fight, Arthur overcame Bradley Rea by divided decision in a excellent all-Manchester contest to secure the continental championship.
The arena fell silent for a profoundly moving memorial before the fight as a bell ceremony tolled in honor of the city's native Ricky Hatton, who succumbed aged 46 in recently.
It was the initial significant broadcast match card in the location since Hatton's passing. As the final chime faded, the quiet transitioned to a roar of "only one Ricky Hatton".
The action within the ring matched the sentiment. Arthur was floored by a left hook squarely on the chin in the initial stage, rising shakily to his position on the referee's count.
But the red-colored attire of the fighter soon advanced again. On the opposite side, Rea - in opposing blue - was damaged soon, significant bruising forming under his face as the pair exchanged hard punches.
Rea, twenty-seven, delivered effective strikes but the champion, 34, matched the intensity with powerful upward punches as the action rarely dropped over the full distance.
The victor narrowly won the verdict with judges scorecards of 114-114, 115-113 and wider gap, but each competitor were relentless and full of heart, all the qualities their idol the legend stood for.
