Miller and his wife welcomed Ethan James, who weighed in at eight pounds and 10 ounces, on Thursday. Under Major League Baseball's paternity rules, which came into play last season, Miller is allowed to be away from the team for 24-72 hours.
Figueroa, meanwhile, joins the A's for a third time this year and gives the team four left-handers in a bullpen that has allowed just one run in 23 innings spanning seven games in the month of July. The 26-year-old posted a 1.04 ERA in six appearances with Sacramento following his June 21 demotion and, overall, has a tidy 1.67 mark in 18 relief outings for the River Cats.
With the A's, Figueroa has a 1.50 ERA in nine appearances, but he's also walked 10 against five strikeouts in 27 innings.
"We've seen a guy that can give us two innings, a guy that can match up against a lefty," manager Bob Melvin said. "We have four lefties down there now, so depending, we can use him in either role. He can give us length. He's a valuable guy to have."