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09/12/11 9:00 PM ET

For Astros' many rookies, a tryout of sorts

HOUSTON -- With so many young players under his guidance -- the Astros have 16 rookies currently on their roster -- manager Brad Mills can use what he sees during September as a way to get a jump-start on some evaluations for next year.

Nearly half of the Astros' 34-man roster is made up of rookies, including 10 rookie pitchers.

"There's no doubt there's some evaluating going on, but at the same time, these guys are learning to be big leaguers and what it's like to pitch against Major League teams," Mills said. "You've got to be able to make pitches, repeat your delivery, repeat that release point. That's what they need to do.

"We've seen some guys in the last two weeks who have struggled in doing that, and they've run into problems. At the Major League level, you're not going to get away with balls coming up in the zone or throwing through your movement on certain pitches. Even for the non-pitchers, these guys have to learn how to make adjustments and learn what it takes to keep their focus where it needs to be."

That being said, Mills said the composition of his bullpen for next year will have more to do with performances during Spring Training than what happens in the final two weeks of the season.

"We've always heard you can't evaluate too much in Spring Training or September, but we can get an idea and we can kind of have our wish list," Mills said. "We want guys to earn spots in Spring Training as we move forward."

Back in Houston, Pence thrilled to see family

HOUSTON -- Phillies outfielder Hunter Pence received a partial standing ovation from the Minute Maid Park crowd when he was introduced prior to his first at-bat on Monday. It was the first appearance in Houston for Pence since he was traded by the Astros to the Phillies in July, as well as the first appearance for Phillies starting pitcher Roy Oswalt, who was traded last year.

Pence doubled in his first at-bat on Monday against former teammate Brett Myers. "It's a good feeling to be back here," Pence said prior to the game. "I love Houston, and I get to go home and see some of my family. I've been looking forward to coming home and playing since that last game [with the Astros] was over in Milwaukee. It's just a good feeling to be home."

Pence, who still makes his home in the Houston area, said the most difficult thing was navigating the logistics of being a visiting player at a ballpark he called home for about five years.

"It's very weird," Pence said. "I'm familiar with the field, but I didn't know how to get to the road clubhouse or where to park or any of that. The whole thing was weird, coming in and saying, 'Man I'm playing against these guys.' It's an eerie feeling."

Pence has picked up where he left off with the Astros; he entered Monday hitting .320 with eight homers and 24 RBIs in 38 games with the Phillies.

"It's the same game," Pence said. "It's just playing baseball. We've got some great veterans, guys with a lot of accomplishments, a lot of achievements. There's an opportunity to learn from great minds in the game of baseball. The quality of veterans [we] have, it's a team that's very professional."

Brian McTaggart is 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.