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8/3/2014 12:10 A.M. ET

Foltynewicz shows heat in Houston debut

Astros rookie pitcher earns high praise from his manager

HOUSTON -- Mike Foltynewicz's second pitch in his Major League debut didn't go as planned. The ball never even reached the dirt, one-hopping from the grass to the catcher's mitt.

Given that his "heart was in [his] stomach" from the nerves, the much-touted prospect was just thankful it came during warmups prior to the eighth inning.

"I have no idea what happened," Foltynewicz said. "It went about 40 feet. I was definitely very nervous."

The hard-throwing right-hander made his first big league appearance in Saturday night's 8-2 win over the Blue Jays, recording two outs in the eighth with a 4-2 lead before walking a third batter.

The nerves didn't show once the hitters reached the box, as Foltynewicz induced a harmless popup in foul territory and recorded a strikeout.

He wasn't doing this against no names, either. The popup? That came against Melky Cabrera. As for the strikeout? Foltynewicz blew three fastballs past Jose Bautista.

"It hit me a little bit, with -- in my eyes -- one of the big-time guys for your debut," he said. "Just tried to go out there and attack them. To get a strikeout is pretty cool."

Foltynewicz threw 12 pitches, all of them fastballs. He reached 99 mph and only one of the dozen offerings was below 96 mph.

According to the rookie, he was just reaching peak velocity when he was yanked after a full-count walk.

"Oh yeah, the adrenaline was definitely kicking in there and I was getting my feet under me and getting the shakes out," Foltynewicz said.

Manager Bo Porter said it was an "impressive" start. But with a two-run lead and a green pitcher on the mound, he felt like he had to go get Foltynewicz.

"I went out to the mound and told him, 'Great job, you've done your part,'" Porter said.

Looking on from the stands as the youngster received a standing ovation on the way to the dugout were Foltynewicz's parents, who were stranded at an airport and missed his first day as a Major Leaguer on Friday after his promotion.

They were there for this one, and Foltynewicz felt it.

"It was really cool they made it," he said. "Really special, because they've been through everything for me. To have this moment finally come, it's one of the top moments in my life."

Though he was a starter through the Minor Leagues, Foltynewicz showed no issues out of the bullpen, where he may stay for much of this season. Porter saw nothing but positive signs from a big arm who could be the closer or setup man of the future in Houston.

"He made quality pitches the entire time," Porter said. "Good to let him get his feet wet. This guy's going to be pretty good."

Guzman set for more tests after back spasms

HOUSTON -- Astros manager Bo Porter said that X-rays taken on reserve infielder Jesus Guzman came back negative after a bout of back spasms forced him out of Friday's 3-1 win over the Blue Jays.

Guzman was moving normally prior to Saturday's game, but he was out of the lineup, hardly a surprise considering he's only started 36 games this season.

"We had to remove him from the game because it spasmed up on him," Porter said. "He could barely move. It locked up on him. Hopefully, he can just continue to move forward."

The injury is similar to an issue that forced the Astros to scratch Guzman from a scheduled start against Chicago on July 20.

"It was almost the same thing," Porter said. "Again, it's not like they can diagnose it beyond just a back spasm."

Further tests are expected, but Porter is optimistic this won't be a recurring issue.

"It comes and goes, because he hadn't had a problem since the time we took him out of the lineup [in Chicago], until last night," Porter said. "That's why they're going to run a bunch of tests, to rule out more causes."

Guzman was 1-for-2 with an RBI single in Friday's game before being pulled after the fourth inning. The RBI was just his eighth of the season, to go along with a pair of home runs and a batting average right at the Mendoza Line.

Gonzalez expected back for finale vs. Jays

HOUSTON -- Despite being out of the lineup for a fourth straight game with a right hamstring issue, Astros shortstop Marwin Gonzalez is expected to be back on Sunday against the Blue Jays.

Manager Bo Porter said Gonzalez would again be available on Saturday for pinch-hitting duty.

This after Gonzalez had a plasma injection on Wednesday in an attempt to alleviate nagging pain in the hamstring, which has given the infielder fits for weeks.

"I'm feeling a little stronger, ready to go and get to play again," Gonzalez said.

Porter said he wanted to use Monday's off-day as a recovery day for the shortstop to assess his physical state following a likely Sunday return.

"Marwin actually could play [Saturday], but when I looked at it, having the off-day on Monday and him getting an extra day today, I wanted him to play tomorrow and have off on Monday," Porter said. "He'll be able to have a good feel for where he is physically."

Prior to the injury, Gonzalez had a four-game hitting streak and had raised his average by 12 points since the All-Star break.

Worth noting

• Rookie George Springer could return as soon as the opening game of the Astros' upcoming road trip starting Tuesday, according to Porter. The manager said he was "optimistic" the outfielder is "close," barring any setbacks with live shagging or baserunning.

Springer has taken batting practice before each of the last five games, including Saturday.

• The Astros will make a decision regarding their fifth starter coming out of Monday's off-day, Porter said on Saturday. Jake Buchanan and Brad Peacock appear to be the most viable options for the role.

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