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8/3/2014 5:45 P.M. ET

Springer will begin rehab stint at Quad Cities

HOUSTON -- The Astros announced after Sunday's 6-1 win over the Blue Jays that rookie outfielder George Springer will begin a rehab assignment with Class A Quad Cities on Monday.

Springer has been working his way back from a left quad strain, and it was even thought that he might rejoin the team in Philadelphia for a series starting on Tuesday.

That seems unlikely now, though manager Bo Porter did hint that the rehab assignment would not last long.

"We want him to go play and make sure everything we see here -- moving around well and going through all the training activities -- is right," Porter said. "We'll re-evaluate after tomorrow."

That indicates that Springer may return from the 15-day disabled list by next weekend, when the Astros face the Rangers at Minute Maid Park.

First, though, the slugger said he needs to test himself at full speed.

"I'm obviously looking forward to live game reps," Springer said. "It's just one of those things, I'll see how it feels [running] and we'll go from there."

Springer said the plan is for him to be in the Quad Cities lineup on Monday, but beyond that, he has no idea of the timetable for his return to the Majors.

Despite missing the last two weeks, Springer is second in the Majors among rookies with 20 home runs since his April callup.

Santana recalled after Guzman lands on DL

HOUSTON -- Domingo Santana isn't making his Major League debut this time, but there's still some career firsts to achieve.

The outfielder will likely get a chance to nab his first career hit after being recalled on Sunday from Triple-A Oklahoma City in place of Jesus Guzman, who was placed on the 15-day disabled list with back spasms.

Santana spent four games with Houston in July, but he struck out 11 times in 13 at-bats, and failed to reach base before the Astros sent him back down.

"It was tough because you reach your goal and you never [believe you will] fail like that," Santana said. "It's good to get a second chance and try to do it again."

Santana hit nearly .300 in his most recent 10 games at Triple-A and actually launched a home run on Saturday prior to being pulled from the game in the seventh inning once his callup was imminent.

Santana arrived in Houston around 10 a.m. CT on Sunday, but he was not in the starting lineup.

"He's been swinging the bat well," manager Bo Porter said before the series finale against the Blue Jays. "Glad that he's back. He's got an opportunity to go to Philadelphia [this week] and play against the team that traded him here. We're excited for him."

Guzman exited Friday's game with back spasms that had caused him problems earlier this season, particularly in a series against the White Sox last month.

Given the Astros' upcoming slate and a banged-up outfield, the club felt it didn't have the roster flexibility to chance Guzman missing several games.

"The determination was more centered around that the last time he had it in Chicago, the number of days he had to miss had us playing short," Porter said.

"We're going into a National League ballpark, where you're thinking about double-switches and pinch-hitters, so that's why we made the move. We just don't have that kind of [5-6 day window] going into a NL park."

Porter said all tests on Guzman, including an X-rays, have come back negative.

Castro keeps it simple in Foltynewicz's debut

HOUSTON -- By now, Jason Castro is used to catching pitchers making their first appearance in the big leagues.

Given his past experiences, Castro had one simple goal for rookie Mike Foltynewicz during the righty's debut on Saturday night against the Blue Jays: keep it simple.

"I know Folty's kind of a level-headed guy and the way he pitched when he was here in the exhibition series was pretty impressive, but the real thing is a little bit different ... My job is to make it as easy as possible for him," Castro said.

It doesn't get any easier than a fastball, which is what Castro called for on all 12 pitches.

Foltynewicz fanned Jose Bautista and got Melky Cabrera to pop out before issuing a full-count walk in two-thirds of the eighth inning, and the last two pitches narrowly missed the plate.

With a success rate like that, Castro saw no need to call any off-speed pitches.

"I saw him in his warmups and his breaking stuff looked pretty good, but I didn't think we needed to use it unless we had to," said Castro, who hit a two-run homer in the Astros' 8-2 win. "The way the ball was jumping out of his hand, I didn't think we needed to change anything."

Castro said if the rookie would have had trouble locating the plate or if, say, Bautista was taking big cuts and barely missing, then they would have turned to secondary stuff.

That wasn't necessary given Foltynewicz's relative effectiveness with fastball-only offerings.

However, it does raise some interesting discussion about his role in the coming years. With a fastball so overpowering, should Foltynewicz remain a bullpen arm instead of a starter?

"He can be [a closer or setup man]," Castro said. "A guy with an arm like that and the way his breaking stuff moves, he's really suited for either one.

"He could move through a lineup with just his fastball and then the second, third time through, get guys out with offspeed and the high-90s fastball in his pocket. That's pretty overpowering."

Worth noting

• Porter said Brad Peacock's experience gives him a "leg up" for the fifth spot in the starting rotation, which the Astros will settle during Monday's off-day. Porter also said they will still keep at least one, probably two long relievers. Paul Clemens, Mike Foltynewicz and Jake Buchanan would be the options for that role.

Chris Abshire is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.