CLEARWATER, Fla. — The Phillies took another hit in the pitching department Monday when they learned that veteran reliever Tommy Hunter would be unable to open the regular season Thursday in Atlanta because of a mild hamstring strain.

Manager Gabe Kapler described it as a "Grade 1" strain in a text message following the Phillies' 6-3 exhibition win against the Pittsburgh Pirates in Bradenton, Fla.

"We do not have long-term concerns," Kapler said. "We're playing this conservatively. We don't have a timetable … at this moment."

The Phillies signed Hunter, 31, to a two-year, $18 million deal during the offseason in an effort to add veteran experience to their bullpen. Hunter will join Mark Leiter Jr. and Jerad Eickhoff — two other anticipated members of the pitching staff — on the disabled list.

In addition to the news about Hunter, the Phillies optioned outfielder Roman Quinn and pitchers Zach Eflin and Zac Curtis to triple-A Lehigh Valley. They also officially released catcher Cameron Rupp a day after designating him for assignment.

Barring a roster addition, it appears as if the 25-man opening day roster will look like this: two catchers (Jorge Alfaro, Andrew Knapp), four outfielders (Rhys Hoskins, Odubel Herrera, Nick Williams, Aaron Altherr), six infielders (Carlos Santana, Cesar Hernandez, J.P. Crawford, Maikel Franco, Scott Kingery, Pedro Florimon) and 13 pitchers (Aaron Nola, Nick Pivetta, Vince Velasquez, Ben Lively, Hector Neris, Pat Neshek, Luis Garcia, Edubray Ramos, Hoby Milner, Adam Morgan, Drew Hutchison, Jake Thompson, Victor Arano).

Jake Arrieta will not be added to the roster until his scheduled regular-season debut April 8.

Extra bases

Kingery continued his scorching spring by going 3-for-4 with a home run against the Pirates. It was his fifth home run and his nine-game hitting streak has boosted his Grapefruit League average to .418. … Velasquez tuned up for his Saturday start in Atlanta by pitching three scoreless innings. He allowed three hits, walked one and struck out three. He finished the spring with a 2.51 ERA in five starts.