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3/9/2014 5:00 P.M. ET

Clemens, eight others sent to Minor League camp

KISSIMMEE, Fla. -- The Astros made their first cuts of camp Sunday morning, reassigning right-handers Jake Buchanan, Bobby Doran, Jason Stoffel and Nick Tropeano, infielders Jonathan Meyer and Ronald Torreyes and outfielders Leo Heras and Preston Tucker to Minor League camp. They also optioned right-hander Paul Clemens to Minor League camp.

Most of the players who were sent out didn't have a realistic shot to make the Major League club and were in camp to be around big league players and get familiar with the staff.

That can't be said for Clemens, who went 4-7 with a 5.40 ERA in 35 games (five starts) for the Astros last year and was in the mix for a spot on the pitching staff. He had pitched in only two games this spring, allowing six hits and three runs in three innings, but the Astros want him to get stretched out and work on fastball command.

"Paul has had mixed reviews at the big leagues," general manager Jeff Luhnow said. "There's been times when he's been very good and times when he's been inconsistent. We just need him to go get steady innings down in the Minor Leagues, and we're having trouble right now finding innings for everybody. We still see Paul as a starting pitcher. We want to stretch him out, and the best way for us to do that right now is at the Minor League level."

With starting pitchers going longer in games and with so many position players in camp, the Astros were still having trouble spreading around the at-bats, which is why they made the moves. Minor League camp has begun in earnest, and games begin on Friday.

"Like I said to all those guys we talked to today, there comes a point in spring from a starting pitching standpoint and from a pitching standpoint, the innings start to get scarce and these guys are a part of our plans down the road and you want to give them an opportunity to get themselves ready for their season," manager Bo Porter said. "From a position-player standpoint, the position players are going to start to play deeper into games, which is going to minimize the number of at-bats we have to go around, and we need those guys to get regular playing time."

The moves leave the Astros with 56 players in camp.

Reviewed call goes against Porter, Astros

KISSIMMEE, Fla. -- For the second day in a row, Astros manager Bo Porter challenged a call on the field. And for the second day in a row, the call was upheld via instant replay.

In the eighth inning of Sunday's game against Toronto, Porter challenged a play at the plate in which Steve Tolleson of the Blue Jays slid home ahead of the tag of catcher Carlos Perez to score the go-ahead run on a Erik Kratz double. The play was close, but the umpires used instant replay to uphold the call.

"Unlike the one yesterday, the one today is one you challenge 100 percent of the time," Porter said. "Just looking at the magnitude of it. ... It's the run that puts them ahead and you have a man on third base with less than two outs. You look at all the parameters of the situation, and if it's remotely close, it's one you challenge."

On Saturday, Porter challenged a call at first base in the second inning, claiming Yankees second baseman Eduardo Nunez hadn't touched first base before Jonathan Villar stepped on the base. Villar was called out after putting down a sacrifice bunt. That call was also upheld.

Sunday was the second of five scheduled Astros games in the Grapefruit League in which instant replay will be used in preparation for its introduction in the regular season. The other Astros games with replay are Wednesday vs. Washington, Friday vs. St. Louis and March 24 against Atlanta.

Porter: Struggling Singleton has quality at-bats

KISSIMMEE, Fla. -- First-base prospect Jon Singleton, who was in the starting lineup Sunday against the Jays, has been off to a rough start at the plate this spring. He was 0-for-15 with three strikeouts after Sunday, though he had drawn six walks.

Singleton is in a wide-open battle for the starting first-base job with Brett Wallace, Jesus Guzman, Japhet Amador and Marc Krauss, who's had a terrific spring so far.

"I think he's taking quality at-bats," manager Bo Porter said. "The one thing in which Jon and I talked about and [hitting coach John Mallee] is going to get with him today -- he doesn't have to over-swing. You're talking about a guy with tremendous power and he has power to all fields. When you [try] to hit the 500-foot home run instead of hitting the ball hard, sometimes you can miss pitches that you probably could hit.

"Overall, I think his at-bats have been good. I think he's over-swinging right now, trying to make something happen."

Porter said it's not uncommon for young players, especially those with the kind of power potential that Singleton possesses, to try to do too much in their first Major League camp.

"You get here and want to impress and show what it is you can do, and as you become a more veteran-type player, you let the game come to you a little bit and allow your ability to play," Porter said. "With conversations with myself and some of the coaches, I think that will improve as spring continues to go along."

Astros excited about top of the order

KISSIMMEE, Fla. -- You can't blame manager Bo Porter for being giddy about the potential of the three hitters at the top of his lineup -- center fielder Dexter Fowler, second baseman Jose Altuve and catcher Jason Castro.

The first inning of Saturday's loss to the Yankees provided a glimpse of what the three hitters are capable of, with Fowler leading off with a single, Altuve moving him to third on a hit-and-run single and Castro smacking a two-run double to left field.

The Astros moved Altuve, who was their best player in 2012, all over the lineup last year, because they didn't have a prime leadoff hitter. The acquisition of Fowler in a trade with the Rockies allowed them to plug Altuve into the No. 2 spot, where he could flourish.

"I said it openly at the beginning of camp last year ... you have to have a guy in front of him who's going to be on base, that can steal a base, that understands situational baserunning," Porter said. "Frankly put, we didn't have that on our team last year, which made it tough to slot him [at No. 2] and keep him there. If you don't have that guy, you're better off putting him in the one hole and get some extra at-bats."

Altuve should see more fastballs from the two-slot with a base-stealing threat like Fowler on base ahead of him.

"It's a pretty good combination of having a guy who was on base at a high percentage and a guy hitting behind him who can really handle the bat," Porter said. "It can really put a lot of pressure on the other team. That's why I love having those two guys at the top of the lineup."

Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.