Selwood said it was a "huge honour" to be named captain and he was "shocked" when informed earlier on Monday.
But the three-time premiership star, who earned his third All Australian selection alongside three of his Cats teammates, said Fremantle was unlucky to have just one player named in the side announced on Monday night.
Despite having five players in the 40-man preliminary squad, Dockers defender Michael Johnson was the only played selected in the final team.
Although saying it was difficult to leave players out, Selwood was glowing in his praise of a Fremantle outfit that beat his Geelong side in the first week of the finals.
"They've had an outstanding year," Selwood said.
"Who do you take out to put in? I think Nat Fyfe has had an outstanding year, David Mundy, and the list goes on.
"They're starting a juggernaut over there. They're hard to stop and we're just hopeful we get another chance."
Selwood said Steve Johnson was slightly unlucky from his own team, but as with the Dockers, it was hard to fit everyone in.
"You look back and you feel pretty safe and you look forward and you feel pretty safe. It's a pretty strong side," he said.
Selwood had three teammates in the 22, with first-timer Andrew Mackie, two-time All Australian Harry Taylor and five-time selection Corey Enright, who is battling a hamstring injury to be available for Friday night's preliminary final against Hawthorn.
The Cats skipper said Enright had been working around the clock and was "absolutely" still a chance of playing.
He nominated Shane Kersten, Josh Caddy and Jordan Murdoch as the players at the head of the queue if Enright did not come up, or if the club chose to accept Paul Chapman's one-match ban for his high bump on Port Adelaide's Robbie Gray.
Whoever might come in, Selwood was confident the Cats could extend their winning streak over Hawthorn to 12 matches.
"We feel like we match up really well," he said.
"There's stars on every line and it's just the ability of winning the hard contest enough times throughout the game.
"We've brought young guys in that have really risen to the challenge that these guys have set before like (captains Tom) Harley and (Cameron) Ling and now we're asking these young kids.
"It's a very important game for us, we love playing against these blokes and you just have to carry on the tradition."
