The Chicago Cubs and the Arizona Diamondbacks recently discussed the feasibility of a trade that would have sent right fielder Justin Upton to the Cubs, according to two major league sources.

According to both sources, the Diamondbacks asked for two-time All-Star Starlin Castro in return for Upton. The Cubs, trying to build a solid base of young players in their somewhat depleted system, balked at trading a 22-year-old shortstop for a 25-year-old right fielder and cut off talks.

Upton, who has been offered around baseball in trade conversations since the winter meetings in December, vetoed a trade to the Seattle Mariners 10 days ago. While the Diamondbacks appear to want to deal him, general manager Kevin Towers said last week that they expect quality in return.

"We are not interested in giving away any of our young talented players," Towers said last Saturday at the Professional Scouts Foundation dinner in Los Angeles. "My job is to get the best players in order to win championships here in Arizona. That said, someone will have to give us equal value if we move one of our top players."