A cut above Eubank Jr's right eye sustained in the third round hampered him for the remainder of the contest and though his record of never being stopped in the professional ranks continued, the judges awarded the fight 117-112, 116-112 and 115-113 in Groves' favour.
Today's bout also represents the semi-final of the World Boxing Super Series, meaning the victor gets a date against either Callum Smith or Jurgen Braehmer come May.
But Eubank Jr starts as the slight favourite.
The tournament's No 1 seed showed his size, experience and skill, controlling the pace from the start and dealing with nearly everything Eubank Jr threw at him, even in a frenetic finish that saw Groves dislocate his shoulder.
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The collision was such that the daredevil's goggles came flying off and he lay on the ground for a few moments in pain and shock. He also had another crash in which he fractured a joint and tore four ligaments in his left shoulder in 2013, per his profile .
The two Britons meet in one of the most highly-anticipated British boxing match-ups in years, with two world titles on the line.
By that stage both fighters were starting to tire but Groves dismissed any notion that he would struggle to go the full distance and was comfortable absorbing more rough tactics as Eubank Jr become desperate.
Although more of the general public are piling in on Groves, it's Eubank Jr who is attracting the bigger stakes.
It was the challenger who suffered though, an accidental head clash opening a sizeable cut on the side of his right eye.
"I told him he's not ready".
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"Did I underestimate him?"
Eubank Jr's father offered a frank assessment of his son's performance.
Your other option is to live stream Groves vs Eubank Jr online via TVPlayer. He cut me, and I couldn't see. A curt, clinical counter hook seemed to put Eubank Jr down, only for referee Michael Alexander ruling out a knockdown. He wasn't dabbing at it so I don't think it was obscuring his vision. I didn't get hit clean.
It's hard to say for sure when Groves and Eubank Jr will enter the ring, but as a rough guidance, it's unlikely to be before 10pm, so there's plenty of time to sink a few Saturday night beers in the build-up.
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