Phelps, 30, has a 3.45 ERA, 1.340 WHIP and has 51 strikeouts in 47 innings this year. He will be a free agent following the 2018 season.
The top prospect the Marlins will receive is 19-year-old outfielder Bryan Hernandez. MLB Pipeline has Hernandez, whom received a $1.85 million signing bonus back in 2014, as the Mariners No. 6 prospects while Baseball America doesn’t have in the top 10.
AJ Ramos, the Marlins closer, is also getting significant interest from contenders looking for a back of the bullpen option.