By Bruce Levine–

NEW YORK (CBS) — The Starlin Castro who walked into the Cubs clubhouse for the first time in May 2010 isn’t much different than the guy who helped lead the Cubs to a furious 50-25 finish to the 2015 season.

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Castro was 19 on May 7 of that 2010 season, when he went 4-for-5 with a homer and six RBIs in his MLB debut. He quickly became the best player and a three-time All-Star on a team and franchise that would only spend 12 days in the ensuing five years over .500. In other words, winning was never something that resonated for Cubs players during that period of time.

Castro has learned what winning and real baseball fun is all about this season under manager Joe Maddon.

On Aug. 6, Castro he lost his job as starting shortstop to rookie Addison Russell. Three days later, he began his career as the team’s platoon second baseman. Three weeks after that, Castro won the job outright and hit .410 in the month of September.

The struggles were tough on him at times. An ego hit like losing your job at 25 would have sent most young players into a frenzy and forced a confrontation with the manager and front office. Through the positive reinforcement of the Cubs and the sage advice given Castro by his agent Paul Kinzer, he stayed above-board as a player and teammate.

“It was tough, but playing with these guys and winning together was the most important thing,” Castro said. “(John) Mallee and the coaches helped me a lot with my swing and confidence. He and Joe talked to me about how I was important to the team. That meant a lot.”

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For two seasons, Castro and first baseman Anthony Rizzo were the only run producers in the lineup. That duo had a rough time driving in 80 runs with little support around them.

“We had good guys and players who played hard,” Castro said of former teammates. “That is nothing to what we have now. These guys can all beat you with one swing. They have added a lot to our team and I am happy to be a part of it.”

Manny Ramirez was hired by the Cubs last season as a player and coach. This season, you can see his impact on Castro and the other young hitters in the organization.

“Manny has been great for all of us,” Castro said. “He helped me stay confident, and his knowledge of hitting is unbelievable. He has helped all the young guys a lot.”

Castro’s name was out there on the trading block in August. It appears now he has a home again in Chicago. Castro will most likely project out to being a third baseman as he matures and his body gets thicker. You can see more power in his swing, now more than any time in the past.

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Bruce Levine covers the Cubs and White Sox for 670 The Score and Follow him on Twitter @MLBBruceLevine.