Mets RH reliever Anthony Swarzak (left oblique strain) threw a bullpen session on Tuesday in Port St. Lucie as he continues to work his way back.
The earliest he can return is May 31.
"He's progressing nicely," manager Mickey Callaway said last week. "We're hoping to get him in games and get him going so he can get back here and help us."
Callaway noted that the team views Swarzak as a pitcher who will be used in a variety of spots upon his return, including high-pressure situations.
"We look at him as a guy that can get righties and lefties out in any situation from the fifth inning on," he said.
The 32-year-old Swarzak, who has been out since April 1 and is on the 60-day DL, signed a two-year, $14 million deal this offseason.
He had a 2.33 ERA (2.74 FIP) and 1.03 WHIP with 91 strikeouts (a career-high 10.59 K/9) in 77 1/3 innings (70 games) last season for the White Sox and Brewers.