The Mariners placed Santos on the 15-day injured list Friday with right knee inflammation.

Santos was sent to Triple-A Tacoma on April 16 but is listed on the major-league injured list. He won't be eligible to return until May 10, and right now it's unclear if his knee will keep him out for more than the 15-day minimum.

Cousins (elbow) is targeting a return in early-to-mid June, Gary Phillips of the New York Daily News reports.

Cousins will throw another bullpen session Friday and is about two weeks away from facing hitters. He'll need a rehab assignment at some point after that. The reliever is recovering from a right elbow flexor strain.

The Royals optioned Sisk to Triple-A Omaha on Friday.

The left-hander was called up from Omaha on April 13 and made his first two MLB appearances while up with the Royals, striking out five with two hits and two walks across 2.1 scoreless innings. Sisk had a 1.56 ERA in 59 outings for Omaha last season and is likely to receive another look with the Royals at some point this year.

The Royals optioned Bowlan to Triple-A Omaha on Thursday.

Bowlan was up as the 27th man for Thursday's doubleheader against the Rockies but didn't make an appearance. He's permitted four runs with a 12:5 K:BB over 12 innings at Omaha this season.

The Tigers recalled Guenther from Triple-A Toledo on Friday, Evan Woodbery of MLive.com reports.

He's absorbing the roster spot vacated by Bailey Horn, who was optioned to Toledo on Thursday. Guenther got a late start to the season due to lumbar spine inflammation, but he's being summoned after allowing three runs over his first 3.1 innings in the minors.

Fairbanks earned the save in Thursday's 7-4 extra-inning win over the Diamondbacks after allowing one walk in a scoreless 10th inning. He struck out one.

It didn't appear initially that Fairbanks would be in action Thursday, but the Rays scored a run in the ninth inning to force extras and plated three more in the 10th to create a save opportunity for the closer. Even though the hard-throwing right-hander has a concerning 1.50 WHIP and 9:6 K:BB over 9.1 innings, he's converted each of his first four save chances and has a 2.89 ERA. Fairbanks' control issues could eventually come back to haunt him, but he has some decent stability as Tampa Bay's No. 1 option for saves coming off back-to-back 20-save campaigns.

Jackson (0-2) was charged with the loss and a blown save in Thursday's 4-3 loss to the Athletics, giving up two runs (one earned) on two hits and one walk in one inning. He struck out one.

Jackson entered the game with a runner on base in the eighth inning and put out Brent Rooker to protect a 3-2 lead, but trouble arose in the ninth frame. The first of his two runs allowed was unearned due to a Leody Taveras fielding error, but Jacob Wilson's walk-off single saddled Jackson with his first blown save of the year. The veteran right-hander has still converted seven of his eight save chances to go with a respectable 3.60 ERA, 1.20 WHIP and 7:3 K:BB over 10 frames, so he figures to remain the favorite for ninth-inning work in Texas' bullpen for the time being, despite Thursday's showing.

Horn was optioned to Triple-A Toledo on Thursday.

Horn was recalled to the majors Saturday and appeared in a game Tuesday, completing 1.1 innings while striking out two. He will likely have the chance to contribute out of the big-league bullpen later in the campaign.

Jansen secured the save in Thursday's 4-3 win over Pittsburgh after allowing one hit in a scoreless ninth inning. He struck out one.

Jansen poured in 14 of his 18 pitches for strikes, and he got Oneil Cruz to line out to end the game while the possible tying run was on first base. The 37-year-old right-hander has looked very sharp in the early going, giving up just five hits and two walks with eight punchouts while converting each of his six save chances over eight shutout innings to open the campaign. With Ben Joyce (shoulder) also on the injured list, Jansen is being relied upon even more for high-leverage work.

Bautista collected the save in Wednesday's 2-1 win over the Nationals, allowing one hit while striking out a batter in a scoreless ninth inning. He did not issue a walk.

Bautista was brought in for the ninth inning to protect a one-run lead. He needed 19 pitches (12 strikes) to make it through the frame, highlighted by a four-pitch punchout of James Wood to open the ninth. Bautista has earned a save in three of his last four outings and has not yielded a run over his last five games.