UK light-heavyweight Joshua Buatsi earned a win yet unimpressive beginning to his career under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a majority decision in a tight ten-round fight at the Co-op Live Arena.
But the challenger found success, landing some telling single shots in a match where the styles didn't complement each other, with excessive holding disrupting the fight.
Two judges had it 96-94 to the winner, with the third a 95-95.
"It wasn't my greatest performance but what do champions do? They succeed," the victor commented in the ring as he was met by negative reactions from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Several boxing experts felt the challenger, 31, deserved the decision but the contender experienced the second loss of his 28-match career.
The Champion Secures Triumph in Uneventful Match
His career development has slowed in the past few years through management issues and long spells of inactivity.
Once tipped as the future of the British fight scene, he now is positioned trying to achieve expectations - possibly in what appears to be a last chance - under fresh management.
He opened tentatively, with the two boxers prepared to overcommit in a cagey initial rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second fight at light-heavyweight.
By the halfway stage, the underdog had kept it close, causing problems for Buatsi, who operated with a tight guard to barely take the cleaner stanzas.
The spectators' acceptance diminished because of regular grabbing, with Parker going down various instances during grappling.
The underdog ended stronger, but many rounds were challenging to assess. However, previous titleholder the boxing analyst - working with Dazn - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi progresses, but with the presence of power puncher Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still looks steep.
Hatton Memorial Motivates Local Rivalry Contest
In the supporting bout, Lyndon Arthur beat Rea by close verdict in a outstanding Manchester vs Manchester battle to win the European light-heavyweight title.
The arena became quiet for a deeply poignant memorial prior to the bout as 10 bells tolled in honor of the city's native Hatton, who succumbed 46 years old in last month.
It was the premier televised boxing event in the city since Hatton's death. As the concluding sound ended, the quiet transitioned to a shout of "only one Ricky Hatton".
The fighting inside the ropes matched the feeling. Arthur was knocked down by a powerful punch squarely on the chin in the second round, getting up unsteadily to his feet on the eight count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. Across the ring, Rea - in opposing blue - was marked up soon, noticeable damage forming under his orbital area as the fighters traded hard punches.
Rea, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with effective uppercuts as the pace seldom decreased over the full distance.
The victor edged the result with judges scorecards of draw, narrow lead and 115-112, but each competitor were persistent and courageous, everything their hero Hatton stood for.
