The Mariners will be short one reliever come Opening Day as tests have revealed that middle reliever Josh Kinney has a stress reaction in his left ribcage, reports Greg Johns of MLB.com.

A stress reaction is often a precursor for a full-blown fracture, so the Mariners have shutdown Kinney to prevent the injury from getting any worse. The 33-year-old right-hander will be sidelined for "several weeks" before the club re-evaluates his condition late in the month.

A five-year MLB vet, Kinney posted a 3.94 ERA and 10.1 K/9 rate in a career-high 32 innings for the Mariners last season, his first in Seattle. His success in 2012 -- all of which came from July onwards -- earned him a spot in this year's 'pen, though he'll obviously have to wait a while before joining the late-inning crew.

Johns speculates that Kinney's absence gives veteran right-hander Kameron Loe a good shot of starting the season in the bullpen. Signed to a minor-league deal with the M's last month, the 31-year-old Loe could provide the relief corps with the veteran presence they lack with Kinney on the sidelines.

Loe owns a career 4.36 ERA and 5.7 K/9 rate in 542⅓ innings over eight seasons with the Brewers and Rangers.