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6/29/2014 2:22 A.M. ET

Mariners set to call up Walker for Monday start

Club's top prospect to make season debut in Houston after finishing rehab stint

SEATTLE -- Taijuan Walker, one of the top pitching prospects in baseball, is expected to make his season debut for the Mariners on Monday in Houston, Seattle manager Lloyd McClendon said Saturday night.

Walker, 21, is the Mariners' top prospect and ranked fifth among all Major League prospects by MLB.com. He pitched three games for Seattle late last season and was expected to land a rotation berth this spring before running into shoulder issues.

The hard-throwing right-hander has started six games for Triple-A Tacoma, going 2-1 with a 4.11 ERA, and is coming off his best outing, a four-hit shutout of Oklahoma City on Wednesday.

"As of now, if all goes well and it's not official, but we'll start Walker on Monday and a move is pending," McClendon said after the Mariners dropped a 5-0 decision to the Indians.

Walker will need to be recalled from Tacoma and added to the 25-man roster to take the rotation spot that opened up when Erasmo Ramirez was sent down after his last start on Wednesday. Reliever Brandon Maurer was recalled to temporarily fill that roster spot and has thrown three scoreless innings with six strikeouts.

Walker faced the Astros in two of his three starts with Seattle last year, going 1-0 with a 1.80 ERA while allowing seven hits with two walks and 10 strikeouts in 10 innings. He was 1-0 with a 3.60 ERA in his three starts in 2013, facing the Royals in his other no-decision.

Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.