The 40-year-old Sierra had an MRI test before Monday's game
against Seattle, which revealed the damage. He was placed on the
15-day disabled list on Sunday after hurting himself the day before
while swinging at a pitch.
The Twins said Sierra will rehabilitate the injury without
surgery and that he should be able to return this season. Signed as
a pinch-hitter and backup outfielder, Sierra strained his right
quadriceps in spring training and missed a month. He batted .188 in
16 at-bats with two RBI before getting hurt again.