Groves: DeGale is getting worse
Groves, 24, beat DeGale on points last year and claims that his superiority over the 26-year-old in the ring has robbed him of his self-confidence.
DeGale has won all three of his fights since that clash at the O2 Arena in May 2011 and on the line against Zuniga this weekend is a WBC silver super-middleweight title.
But should DeGale come out on top, Groves is unlikely to change his stance on his foe's form, citing the short time Zuniga has had to prepare for the fight in Hull on Saturday.
"Since fighting me he hasn't impressed much -- he's a confidence fighter and I took away all his confidence," Groves, who defends his commonwealth belt a week later, told the Sun. "He also hasn't been fighting the right opponents.
"His next guy seems good on paper but he only took the fight at a week's notice."
In September, DeGale insisted he had got the 'buzz' back ahead of his successful fight with Hadillah Mohoumadi but ruled out a rematch with Groves in the near future.