The status of the three are pending physicals before they are announced. The Marlins have not confirmed the deals.
Miami’s front office is tasked with finding players with either big league experience or ones who are considered close to being big league ready in the aftermath of the club having been hit hard by the coronavirus pandemic.
The team’s traveling party has been in Philadelphia since July 23, where they are being tested for COVID-19 daily.
On Friday, another positive test result was confirmed, raising the total to 18 players, and two coaches.
MLB announced on Saturday that the Marlins are set to resume their season in Baltimore from Tuesday through Thursday, with one day including a doubleheader (all game times TBD) and the Marlins serving as the home team for two games.
In addition, the originally scheduled games between the Phillies and Marlins from Aug. 4-6 will be rescheduled for a later date. The club last played Sunday at Citizen Bank Park, where it took two of three from the Phillies.
Venditte, who is a switch-pitcher, was in Spring Training with the Marlins as a non-roster invitee. But he was not part of Miami’s initial 60-man player pool.
Castillo, 36, appeared in two games with the Marlins in 2019, but he spent most of the season at Triple-A New Orleans, where he played in 58 games.
Forsythe, 33, has played in nine seasons, last year with the Rangers.
As the Marlins’ traveling party awaits clearance to leave Philadelphia, workouts and daily COVID-19 testing has been going on at the club’s alternate training site in Jupiter, Fla. The new additions will be reporting to the Roger Dean Chevrolet Stadium complex to begin working out.
Based on the additions of four new relievers, bullpen depth has been a primary focus for the Marlins. They’re also in need of potential starting pitcher candidates.
Currently on the injured list are right-hander José Ureña, catcher Jorge Alfaro, outfielder Harold Ramirez and first baseman/designated hitter Garrett Cooper.
Based on their high number of positive tests, the Marlins’ injured list is expected to grow by at least 15 once they finalize roster moves. When players are placed on the injured list due to COVID-19, the team is permitted to add players to the 40-man roster to take their place while they are out.