Keeffe will step up as the No.1 ruck for the Giants after Briggs suffered a concussion in their opening round win over Collingwood.
Briggs was stretchered off the field against the Magpies and taken to hospital wearing a neck brace after a collision with teammate Sam Taylor in the first quarter.
The Giants are yet to determine a time for the ruckman's return, as they look ahead to meeting Melbourne on Sunday at the MCG.
Keeffe was outworked by Collingwood big man Darcy Cameron with 12 hitouts to 37, but his resolve was praised by GWS coach Adam Kingsley.
He shared the ruck load with young key forward Max Gruzewski (six hitouts).
"'Briggsy' is obviously a big piece of our team, how we go about it," Keeffe told AAP.
"He starts us off in the middle. He's got great contests, great hunt. He's a big man and he gives us first use.
"Darcy Cameron is a pretty good player and I think he taught me a little bit of a lesson.
"I just try to stay strong in the contest and give what I can for the team."
Keeffe was handed the No.1 spot late last season after Briggs was managed out of their round 22 clash against Brisbane with a sore shoulder.
He remained in the Giants side throughout the finals to play a total of five games last season, earning a one-year contract extension, but was then de-listed only to be re-drafted by the Giants as a rookie.
No stranger to doing it tough, the 34-year-old won't shy away when he comes face-to-face with seven-time All-Australian ruckman Gawn.
"Max has been the best ruckman probably of our generation - it's going to be a test," Keeffe said.
"I'll do my best for my team. I don't expect to be Max Gawn or Kieran Briggs but I'll give it a crack.
"I'm definitely not Briggsy, but I throw my hand up, play my role for the team, whatever it is."
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