Grover, seen last year as Fremantle's third tall option in defence, shapes as an obvious replacement for Tarrant in 2011, with Luke McPharlin and young pair Alex Silvagni and Peter Faulks rounding out the club's tall backline options.
Tarrant, who revived his career at Fremantle as a full-back, returned to Collingwood during last October's trade period after consecutive top-10 finishes in the club's best-and-fairest award, and Grover said no one person would cover his loss.
"As a backline as a whole we're going to have to step up," Grover said on Friday morning.
"Chris Tarrant's left the club now so we look forward and we move on.
"[Silvagni] has been tracking really well and we've got Peter Faulks coming through. He looks like a good type.
"So it's also for me and Luke McPharlin to be passing on our knowledge to these guys coming through."
Grover played 14 games last season after suffering a medial ligament injury late in the pre-season and missing the first eight rounds.
He said his preparation for 2011 had been uninterrupted and he would enter the new season fitter and slimmer as a result.
"The body's the best it's been for a long time," he said. "I've got through most of the pre-season if not all of it and I'm feeling good.
"I've probably found you get older and you learn to look after your body the best you can.
"I've had no off-season operations, which puts you in good stead, and I've been able to do some running in the off-season and also in the pre-season.
"With the new interchange rules and so on we're trying to get fitter and faster, and every club says they're doing the same thing at the moment.
"The game's really demanding these days, so it doesn't matter where you play you've got to be able to cover the ground."
Grover and Silvagni were the only key defenders named in Fremantle's squad to take on Adelaide at Thebarton Oval on Saturday afternoon, with goalkicking recruit Jack Anthony another option.
Key midfielder David Mundy and ruckman Aaron Sandilands were also left out of the squad, as were youngsters Nat Fyfe, Stephen Hill and Dylan Roberton, who are yet to play this pre-season.
Fremantle travelled with new AFL carrier Virgin Blue for the first time on Friday morning and Grover said he was unconcerned by the change from Qantas.
"I don't think the airline really matters, it's more of a case of the young blokes that haven't travelled a lot getting into a routine," he said.
"To travel probably 10 times in the year, it's very important that we not only get our routines right, but [that] we do get looked after when we travel."
