UK light-heavyweight Joshua Buatsi made a winning yet unimpressive beginning to his career under fresh promotional backing with a unanimous decision over Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a close 10-round bout at the Manchester venue.
But Parker had his moments, connecting with powerful individual punches in a fight where the techniques never quite clicked, with constant grabbing disrupting the contest.
Two judges scored it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my best display but what defines champions? They win," Buatsi said in the ring as he was met by boos from the crowd.
The Londoner bounced back after his initial pro loss - an epic battle with his previous opponent in last winter - to claim a 20th career victory.
Some ringside observers thought the challenger, thirty-one, should have been awarded the victory but the contender experienced the second setback of his 28-match career.
The Champion Claims Win in Uneventful Match
Buatsi's progress has plateaued in recent years through management issues and extended periods of inactivity.
Once tipped as the next star of the British fight scene, he now finds himself trying to realize his potential - possibly in what appears to be a final roll of the dice - under recent support.
He started carefully, with neither fighter willing to overcommit in a tentative opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after breaking his hand in the contest, was participating in his second bout at light-heavyweight.
By the halfway stage, the underdog had kept it close, creating difficulties for the favorite, who operated with a solid defense to narrowly win the better periods.
The crowd's patience wore thin amid frequent holding, with the challenger slipping to the canvas multiple occasions during grappling.
Parker ended stronger, but many rounds were challenging to assess. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just only one stanza.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Homage Inspires Local Rivalry Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific all-Manchester fight to win the European light heavyweight belt.
The arena fell silent for a deeply poignant tribute before the fight as ten bells tolled in memory of local hero Ricky Hatton, who succumbed at age 46 in recently.
It was the premier televised boxing event in the urban center since the passing of Hatton. As the last bell ended, the stillness transitioned to a shout of "there's just one Hatton".
The fighting inside the ropes reflected the emotion. Arthur was sent to the canvas by a significant blow squarely on the chin in the early round, standing uncertainly to his footing on the eight count.
But the red-colored shorts of the fighter soon pressed ahead again. Across the ring, the opponent - in opposing blue - was damaged quickly, noticeable damage forming under his face as the fighters landed powerful shots.
Rea, 27, landed power punches but Arthur, 34, responded in kind with effective uppercuts as the intensity seldom decreased over 12 rounds.
Arthur edged the decision with scoring tallies of 114-114, 115-113 and 115-112, but both fighters were persistent and brave, everything their hero Hatton stood for.
