The Cats handled the Dockers with ease at Optus Stadium to sit atop the summit of the ladder for the time-being, with Fremantle's finals credentials now heavily questioned.
Their bid for a top-eight finish received collateral in the loss, with the in-form Darcy having his night ended following a dominant display in the middle of the ground.
The 23-year-old managed 18 disposals, eight clearances and 37 hit-outs before succumbing to a knee injury late into the match.
Lobb was subbed out of the game at half-time with a reported syndesmosis injury, with youngster Brandon Walker coming into the game.
The pair of injuries place further headaches to coach Justin Longmuir, who is currently without key-forward Matt Taberner through injury.
Speaking post-game, Longmuir said the club will await the results of scans for Darcy and Lobb in the next 24 hours.
"We've got a 10-day break and we’ll get them scanned tomorrow. I’m not going to rule them out for next week," he said.
The Dockers could be hit with further damages as tall forward and part-time ruckman Josh Treacy was placed on report during the loss.
"You took a free shot at him." Fremantle's Josh Treacy has been reported for this bump on Geelong's Jed Bews.
— Fox Footy (@FOXFOOTY) July 15, 2021
The 18-year-old found himself in the umpire's book after a late hit on Cats defender Jed Bews during a marking contest.
It is expected that Treacy won't be sidelined through suspension, with a fine the likely outcome of the incident.
The Dockers face fellow finals contenders Sydney in Round 19, with that match scheduled for GMHBA Stadium.