British light heavyweight Joshua Buatsi made a winning yet unimpressive debut to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a close 10-round bout at the Co-op Live Arena.
But Parker found success, connecting with powerful single shots in a fight where the approaches failed to mesh, with constant grabbing spoiling the action.
The scoring judges judged it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my best performance but what defines champions? They prevail," Buatsi said in the ringside as he was met by boos from the spectators.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in last winter - to earn a 20th pro success.
Some ringside observers thought Parker, 31, deserved the victory but the British boxer suffered the second loss of his 28-match professional journey.
The Champion Earns Win in Uneventful Affair
Buatsi's progress has stalled in recent years through promotional disputes and extended periods of inactivity.
Earlier forecast as the rising talent of British boxing, he now is positioned trying to realize his potential - maybe in what feels like a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors ready to overcommit in a cagey opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after damaging his hand mid-fight, was competing in only his second fight at light heavyweight.
By the halfway stage, Parker had kept it close, causing problems for the favorite, who worked behind a protective stance to edge the cleaner periods.
The spectators' acceptance decreased during frequent holding, with Parker going down various instances during grappling.
Parker closed well, but many rounds were difficult to score. However, former world champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, giving Buatsi just one round.
The victor moves on, but with the presence of power puncher David Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Tribute Inspires All-Manchester Fight
In the secondary fight, Arthur overcame Rea by divided decision in a outstanding all-Manchester battle to win the European light heavyweight title.
The venue became quiet for a deeply poignant memorial prior to the bout as ten bells tolled in remembrance of local hero Hatton, who succumbed aged 46 in September.
It was the first major televised match card in the location since Hatton's passing. As the concluding sound disappeared, the silence became a chant of "there's only one Hatton".
The competition during the bout equaled the emotion. The eventual winner was floored by a powerful punch directly to the face in the initial stage, rising shakily to his feet on the referee's count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. From the other corner, Rea - in competitive blue - was damaged quickly, significant bruising appearing under his orbital area as the duo exchanged punishing blows.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with stinging uppercuts as the action seldom decreased over twelve rounds.
The victor narrowly won the decision with scoring tallies of 114-114, close margin and 115-112, but each competitor were relentless and courageous, everything their inspiration Hatton represented.
