Having just been called up by the Astros and set to make his Major League debut, catcher Jason Castro glanced at the lineup card for a game against the Giants on June 22, 2010, at Minute Maid Park and saw his name alongside Michael Bourn, Lance Berkman, Carlos Lee, Hunter Pence and Roy Oswalt.

Castro was one of the Astros' top prospects -- a former first-round Draft pick who was the first selection under the regime of then-general manager Ed Wade and then-scouting director Bobby Heck -- and joined a veteran club that was still trying to contend in the National League Central.

A little more than a month later, Berkman and Oswalt had been sent away in trades, a move that marked the beginning of one of the most aggressive rebuilding efforts the game has seen. Bourn and Pence were traded a year later, and Lee was dealt in 2012.

Castro, meanwhile, watched the team change around him as the Astros acquired waves of prospects while looking toward the future. Less than four years later, Castro, 26, finds himself as the Astros' elder statesman, team leader and reigning All-Star. It's a role he's cherishing as the club begins the climb back to respectability.

"It's been kind of a surreal experience," Castro said. "It's gone pretty fast. I can still remember my first Spring Training, being here with Berkman, Roy Oswalt, Carlos Lee and Geoff Blum, and a lot of those veterans who had been around for a long time. I've kind of come full circle."

The Astros have gone through a lot since Castro made his debut, with the team undergoing an ownership change, a managerial change, a switch to the American League and outfitting itself in new uniforms. Castro, despite missing the entire 2011 season following knee surgery, has remained a rock.

Castro earlier this year signed a $2.45 million contract in his first year of arbitration eligibility, after coming off a breakout season in which he hit .276 with 18 homers and 56 RBIs en route to being named the team's Most Valuable Player for 2013. He was the first Astros player to make the AL All-Star team.

"I give him a lot of credit for working hard and being able to play whatever role necessary," general manager Jeff Luhnow said. "When he was just getting here, he was listening to the veterans and soaking it all in, and now just a few years later, he is the veteran and he is providing leadership to the rest of the team, and it's really important for us to have guys like that who aren't just veterans that come from other teams, but veterans who have been here the whole time."

As he watched waves of established players getting traded, Castro bought into the rebuilding plan set forth by Luhnow, and he knew better days were ahead. His eyes were opened while he was rehabbing from knee surgery in Kissimmee in 2011 and some of the young talent came through the instructional league.

"That was the year George Springer got drafted, and he came to instructs for the first time and I got to see those guys firsthand, and to see where they are now, they've really made a tremendous amount of progress in a short period of time," Castro said.

Springer is one of the club's top prospects, and he's in camp this year along with other up-and-comers like first baseman Jonathan Singleton, shortstop Carlos Correa and pitchers Mark Appel and Mike Foltynewicz. If Castro has any advice for the young guys, it's to work hard.

"That's what really separates guys, and it will determine what guys are able to accomplish," he said. "Obviously, guys can get there purely based on talent, but I think the dividing factor of what keeps guys in the league for many years and extends their careers is how hard they work at it. Guys go about their business the right way, and that's what's nice to see with the young guys here. They already have a good work ethic, and they put in the work needed to get to where they want to be."

Luhnow said several teams called him to ask about acquiring Castro this past offseason, but he said when you put the entire package together -- what Castro does off the field and the leadership he provides and his links to the past -- the organization decided that Castro had too much value.

"We take all of those elements into account, and we really feel he's a player we can't be without at this point," Luhnow said. "I think he's exceeded expectations, even internally for the people that drafted him in the first round. He's a left-handed-hitting catcher with power and good defensive skills. He's been injured here and there, but by and large, he's everything you hope for in a first-round pick."

Castro was made aware of the trade rumors by his wife and his mother, but he was kind of busy this past offseason. He went to Stanford to finish his degree, and was too tied up in homework and term papers to worry about the rumor mill.