By: Kelly Thesier/MLB.com

MINNEAPOLIS — The Twins bullpen was dealt a blow on Friday when an MRI on Jose Mijares’ right knee revealed a torn meniscus and he’ll have to undergo surgery that will keep him out for about four weeks.

That’s still enough time for Mijares to possibly rejoin the team for the end of the season, but it will all depend on how long it takes for the left-hander to recover.Mijares suffered the injury while running to cover first base in the eighth inning of Wednesday’s 6-1 loss to the White Sox in Chicago.

Manager Ron Gardenhire said that without Mijares the club will rely more on left-hander Ron Mahay in a larger role. Glen Perkins will also give the Twins another lefty in the ‘pen in a couple days since he needed some rest after making a spot start for the club on Wednesday. But since Perkins has started all season, it will likely take him some time before he’s able to pitch on back-to-back days.

The Twins will likely explore the trade market to see if they can find any left-handed relief help. Players must first clear waivers before they can be traded or teams can work out deals with another team if they win a waiver claim on a player.

As for Justin Morneau, there is still no timetable for the first baseman’s return. Morneau, who has been working out most days at Target Field, continues to experience some symptoms from the concussion he suffered on July 7 and he has yet to go through a full day symptom-free. That’s something that must occur for multiple days before Morneau can be sent out on a Minor League rehab assignment.

Manager Ron Gardenhire said that the club will take things slowly and make sure that Morneau doesn’t try to rush back and risk suffering more setbacks.