By Bruce Levine–

(CBS) — The Cubs on Wednesday lost their second franchise player to injury in three days. All-Star shortstop Starlin Castro was diagnosed with a high left ankle sprain that will prematurely end his season, keeping him out all of September. Castro suffered the injury sliding awkwardly into home plate in the first inning against the Brewers.

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Cubs general manager Jed Hoyer said that X-rays and an MRI were taken on Castro’s leg, revealing no fractures but a significant left ankle sprain that would take four weeks to heal and rehab. The Cubs’ season has only 25 days and 23 ballgames remaining before the season finale on Sept. 28 in Milwaukee.

The 24-year-old Castro had a resurgent season on the field, hitting .292 with a career-high 14 home runs and 65 RBIs. He also had a breakout season on defense. Through hard work and a supportive group of coaches, Castro cut his errors to a career-low 15. He had led the National League in errors during the 2011 and 2012 seasons.

On Tuesday, the Cubs had lost All-Star first baseman Anthony Rizzo for the season due to a back injury. Both All-Star players are unlikely to return to game action before spring training 2015.

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“We give him a lot of the credit,” manager Rick Renteria said of Castro. “It was kind of his responsibility to change the way people viewed him. I think he has done a really nice job. He has dealt was a lot of different things in a very positive way. After a start that wasn’t all positive, he kept working and kept grinding, his defense started to get better and then his offense began to take off. He worked himself into an All-Star role again.”

Castro was inserted in the cleanup slot of the batting order in late April and stayed there until the injury Tuesday evening. He earned his third All-Star berth in four seasons while raising his batting average by 47 points from a career low .245 in 2013.

Renteria said that rookie Javier Baez will get the majority of the playing time at shortstop over the last three weeks of the season. Baez had been playing second base.

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