OAKLAND -- Rookie right-hander Rogelio Armenteros will be called up from Triple-A Round Rock to start Saturday’s game against the A’s at the Coliseum, Astros manager AJ Hinch said Friday. Armenteros will fill the spot in the rotation that became vacant when Monday’s game against the White Sox was rained out in Chicago, forcing Zack Greinke to pitch on Tuesday instead of Monday.

The Astros will make a roster move following Friday’s game to make room for Armenteros, the club's No. 22 prospect per MLB Pipeline.

Armenteros has appeared in four games for the Astros this year in two different stints, posting a 1.93 ERA in 14 innings. He didn’t allow an earned run in four innings of relief on July 16 at the Angels and held the Rangers to one run on two hits in five innings in his only start on July 21.

The 25-year-old Cuban is 5-6 with a 5.05 ERA in 17 games (16 starts) for Round Rock this year. He threw 6 1/3 hitless innings in his last start for Round Rock on Sunday at Albuquerque.

“He’s thrown very well,” Hinch said. “Righties [perform] better than lefties against [the A's] lineup, and we think he’s the right option for us.”

It’s expected that Armenteros will make only this start before being sent back to Round Rock. Martin Maldonado will start behind the plate to catch Armenteros for the first time.

Cole progressing well
Astros right-hander Gerrit Cole, who was scratched from his scheduled start while warming up before Game 2 of Tuesday’s doubleheader against the White Sox with right hamstring discomfort, played catch prior to Friday’s game, which is his first step to getting back on the mound.

“He’ll do that again over the weekend,” Hinch said. “Our hope is he’s going to be able to pitch at the back end of that Detroit Tigers series [Monday through Thursday in Houston]. In order to do that, he’s going to have to play catch, he’s going to have to throw a very extensive bullpen. We’ll do some agility, PFP stuff with him. The first step was literally playing catch, and he feels really good about it, so that’s a good sign.”

Cole, the American League Pitcher of the Month for June and July, is among the top contenders for the AL Cy Young Award this year, as he's 14-5 with a 2.87 ERA in 25 starts. He leads the Major Leagues with 226 strikeouts and is 10-0 with a 1.98 ERA, 22 walks and 126 strikeouts in his last 14 starts.

Peacock close to return
The Astros appear to be close to activating veteran right-hander Brad Peacock, who threw 16 pitches in one hitless inning during his Minor League rehab assignment Thursday night for Round Rock. He’s been on the injured list since June 28 with right shoulder discomfort.

Peacock (6-6, 4.13 ERA) could be activated by the time the Astros leave Oakland on Sunday. And when he does, he’ll return to the bullpen after being used almost exclusively as a starter the first three months of the season. Since he sustained shoulder discomfort, he’s appeared in six rehab games, including the last five for Round Rock.

Hinch said Peacock played catch in Round Rock on Friday and his shoulder felt good.

“Getting him through a scoreless inning was really important,” Hinch said. “And then we’ll consider anything from bringing him back out here to be activated in this series to possibly joining us [next week at home against the Tigers]. He’ll pitch somewhere again this week, just not sure where.”