Hall hit 35 home runs in 2006 and was rewarded with a $24 million, four-year contract. But he was hitting only .201 with six homers and 24 RBIs in 76 games when the Brewers designated him for assignment last week.
Hall is expected to join the Mariners on Thursday in Detroit. Seattle is on the fringe of the AL wild-card race, and starting third baseman Adrian Beltre is on the disabled list.
The Brewers are expected to pay a large portion of the money that remains on Hall's deal -- more than $2 million this year, $8.4 million next year and a $9.25 million club option for 2011 with a $500,000 buyout.
"We saved some money here," Brewers assistant general manager Gord Ash said, without confirming an exact figure.
"Obviously, when you enter into a long-term deal with a player, you hope it has a much different ending than this one has. But I think that given his ongoing struggles in Milwaukee, this gives him a fresh start and us some limited financial flexibility next year compared to what we did have, and certainly the year after on the buyout of the option, so maybe we can use those resources to address a more important need at the moment," he said.
Flores went 3-2 with 18 saves and a 4.39 ERA in 44 games for two Class A teams.
"He's got a power arm," Ash said. "Not to dismiss his ability, but this is more about trying to secure financial relief than it is about acquiring personnel."
The Mariners said left-handed starter Erik Bedard will be transferred from the 15-day disabled list to the 60-day DL to clear a spot on the 40-man roster for Hall. Seattle's roster is full after it signed second overall draft choice Dustin Ackley to a five-year major league contract on Monday.
Bedard is wearing a cast and brace after surgery last week to repair a torn labrum in his pitching shoulder.