British light heavyweight Joshua Buatsi made a winning yet underwhelming debut to his career under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's activity level likely gained him a split decision in a close ten-round contest at the Manchester venue.
But Parker landed significant shots, delivering effective individual punches in a contest where the techniques failed to mesh, with frequent clinching disrupting the action.
The scoring judges had it 96-94 to Buatsi, with the final judge a even score.
"It wasn't my finest display but what do champions do? They win," the victor commented in the arena as he was faced disapproval from the audience.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in last winter - to earn a 20th pro success.
Several boxing experts felt the challenger, thirty-one, should have been awarded the victory but the British boxer endured the second defeat of his 28-match professional journey.
Buatsi Earns Triumph in Uneventful Match
Buatsi's progress has plateaued in the past few years through promotional disputes and long spells of inactivity.
Earlier forecast as the future of UK boxing, he now is positioned trying to achieve expectations - possibly in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter prepared to overcommit in a cagey initial rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after breaking his hand during the bout, was participating in his second bout at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, creating difficulties for the favorite, who operated with a tight guard to barely take the more effective periods.
The audience's tolerance decreased amid constant clinching, with the challenger going down multiple occasions during grappling.
The underdog finished the stronger, but several stanzas were challenging to assess. Nevertheless, former world champion Carl Frampton - working with the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just one round.
The victor advances, but with the caliber of hard hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Memorial Inspires All-Manchester Fight
In the supporting bout, Arthur beat Rea by divided decision in a terrific all-Manchester battle to secure the European light-heavyweight championship.
The arena became quiet for a extremely emotional tribute ahead of the contest as 10 bells tolled in honor of local hero Hatton, who succumbed at age 46 in September.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the concluding sound disappeared, the silence became a roar of "only one Ricky Hatton".
The action within the ring reflected the sentiment. Arthur was sent to the canvas by a powerful punch squarely on the jaw in the second round, standing uncertainly to his feet on the count of eight.
But the traditional red attire of the fighter soon pressed ahead again. From the other corner, the opponent - in competitive blue - was damaged quickly, significant bruising forming under his orbital area as the duo landed powerful shots.
The challenger, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with stinging uppercuts as the pace seldom decreased over the full distance.
The victor narrowly won the result with official scores of 114-114, close margin and clearer margin, but each competitor were relentless and brave, all the qualities their inspiration Hatton stood for.
