Hardy, who won the show in 2006 with Mark Ramprakash, claimed that viewers would be wrong to presume that the ex-EastEnders star was going to be "the clown" of the series.
Groves and Erin Boag scored 29 points on Saturday for their Paso Doble, with judge Bruno Tonioli describing him as being like "a bull in mating season".
"Erin chose her choreography well. He had to match her arms, he knows his counts... there were a lot of hard moves," Hardy told It Takes Two. "There's lots of hard points in that routine. Those putting Ricky as the clown, watch out!
"He may be giving 100%, but he is also learning. In these early days, Erin will be ticking boxes. Those contestants, like with Rav [Wilding], who just thought we've got a gorgeous guy here, let's just put him out there to pick up points - you can't do that."
She added: "Erin has been very clever, he's already learning how to match arms, he's already feeling confident on his own - big ticks, early days."
Strictly continues at 7pm on Saturday on BBC One.