OAKLAND -- The A's continue to populate flights between Oakland and Nashville.
With veteran Santiago Casillahitting the disabled list Saturday with a right shoulder strain, right-handers Chris Bassitt and Carlos Ramirez were the latest bullpen reinforcements called upon from the Triple-A club. Right-hander Frankie Montas also joined them ahead of his expected promotion Sunday for a start against the D-backs.
Originally scheduled starter Trevor Cahill, afforded an extra day of rest, will go Monday against the Rays.
Montas will be making his season debut for the A's, after pitching to a 4.39 ERA in nine starts for Nashville. He allowed seven runs (five earned) over five innings in his latest start (May 20), but limited the opposition to four earned runs in his previous 20 innings.
"I think based on talking to our people down there, Frankie is pitching pretty well right now," A's manager Bob Melvin said.
Montas struggled out of the bullpen with the A's last year, compiling a 7.03 ERA and issuing 20 walks and allowing 10 home runs across 32 innings. In 41 innings with Nashville this year, he's yielded 13 walks and five homers.
"He's throwing strikes, he's had a couple of good outings," Melvin said. "His breaking ball, obviously, is going to take him where he needs to go. He's got a great fastball, but he was working on his offspeed stuff and throwing that for strikes, and they feel like he has that under control."
Montas will be the ninth different starting pitcher used by Oakland in their first 53 games. Injuries robbed the A's of Paul Blackburn and Jharel Cotton at season's start, and they've since lost Brett Anderson and Andrew Triggs to the DL as well.
Righty reliever Josh Lucas, who made a spot start Thursday, was optioned to Triple-A as part of Saturday's flurry of moves, with the A's in need of another round of fresh arms.
Bassitt -- back for a second stint but still seeking his first big league appearance since 2016 -- ensures them length out of the bullpen, while Ramirez will primarily be used in matchup situations, according to Melvin. Ramirez was claimed off waivers from the Blue Jays just last week and pitched in one game for Nashville on Thursday, fanning three in two innings.
"They liked what they saw in his first outing," Melvin said. "And we need some arms right now."
Casilla, who has a 3.32 ERA in 16 outings, is not expected to be out much longer than the minimum 10 days.

Swingin' A's honored
On Saturday, the A's honored players from the Swingin' A's era in a pregame ceremony. Attendees included Vida Blue, Bert Campaneris, Ken Holtzman, John "Blue Moon" Odom, Joe Rudi, Gene Tenace and Sal Bando, among others.
Melvin, who wears No. 6 in honor of Bando, was behind the plate for Bando's ceremonial first pitch.
"I get nervous around these guys," Melvin said. "These guys were a big part of my youth. What these guys accomplished for this organization resonates for me."