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Craig Stammen, a spot starter and long reliever, is another possibility after being non-tendered by the Nationals.
Cishek, Miami's closer at the start of the 2015 season, lost his role in mid-May and was traded to the Cardinals for reliever Kyle Barraclough in late July.
The 29-year-old, who made $6.65 million, was due for a pay raise in his final season of arbitration. St. Louis opted to non-tender the former closer, making him a free agent.
Although the Marlins are comfortable with their bullpen, Cishek is a homegrown talent who could be primed for a bounce-back season. He has 95 career saves, including 73 with Miami in 2013-14.
Cishek wouldn't be a closer option, but he could find a spot in a setup capacity.
For the most part, the Marlins like their bullpen. On Wednesday night, they non-tendered reliever Aaron Crow, who missed all of 2015 due to Tommy John surgery.
Crow's surgery was in April, and recovery time is about 12 months for a reliever. He was due to make close to $2 million in 2016.
"I would say bullpen arms are an area of depth for us," president of baseball operations Michael Hill said. "To have a player unavailable in an area of depth, it didn't make sense to allocate dollars in that manner either."
Also on Wednesday, the Marlins parted ways with their Opening Day starter, Henderson Alvarez, who underwent right shoulder surgery in July.
• Marlins non-tender right-handers Alvarez, Crow
In arbitration, Alvarez was projected to make about $4 million, and the club wasn't confident he would be ready for at least the first month of the season.
"Given our challenges, we have to have our dollars on the field performing for us," Hill said. "We felt like we could better allocate the dollars in other areas."
Hill said the Marlins are open to signing Alvarez and Crow to lesser offers, if both would agree to return.
Petit, 31, pitched for the Marlins in 2006. The Venezuelan native spent four seasons with the Giants from '12-15 before being non-tendered.
Petit has been effective as a spot starter and long reliever. He appeared in 42 games with one start in 2015 and posted a 3.67 ERA in 76 innings.
But in San Francisco, Petit was caught in a numbers situation and was non-tendered.