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Peoria, AZ (SportsNetwork.com) - Seattle Mariners prized prospect Taijuan Walker's status for making the Opening Day roster is in question after it was announced Friday that the right-hander will be shut down 5-to-7 seven days with shoulder inflammation.

Walker complained of shoulder soreness two weeks ago, but felt good after throwing a bullpen session last week.

The 21-year-old made his much-ballyhooed major league debut on Aug. 30 last season at Houston, earning the win as the Mariners topped the Astros 7-1. He made two more starts in September, resulting in a pair of no-decisions.

Walker threw five innings in all three outings, allowing a total of seven runs -- six earned -- and recording 12 strikeouts.