Washington Nationals outfielder Michael Morse will be shut down for six weeks after aggravating a strained muscle in his back on Monday while playing for Class-A Hagerstown, according to MLB.com.

Morse, 30, was placed on the 15-day disabled list in late March and there is no timetable for his return.

He was given a two-year extension over the winter to remain as the cleanup hitter in the Washington lineup and provide protection for franchise third baseman Ryan Zimmerman.

Last season, his third with the Nats, Morse batted a robust .303 with 31 home runs and 95 RBI.

Over seven major league seasons with Washington and Seattle. Morse is a career .296 hitter with 69 doubles, 52 home runs and 183 RBI in 383 games.

Washington does have options on the bench to replace Morse in Mark DeRosa and Xavier Nady, but could also use the opportunity to call up super prospect Bryce Harper from Triple-A Syracuse.