Walker only made it through the second inning on Saturday night against the Dodgers in Los Angeles. The right-hander told the Arizona Republic the tightness started in the first inning, but he did not feel it as much in the second. But, Walker’s velocity had dipped into the low 90s, and he did not come out for the third inning.
Walker did not seem concerned about his health after the game, but tightness in your pitching arm is never something any pitcher wants to hear and is generally not a good sign. Walker will undergo an MRI on Monday, but he could miss an extended period of time. Tommy John surgery would be the worst outcome, but hopefully, it is just tightness and not a tear of any muscle.
In any event, regardless of whether Walker misses one start or is out longer, the D-Backs will need another starter. Unfortunately, Arizona does not have the best pitching depth, but the team has options.
Here are the most likely candidates to replace Walker in the rotation.
Shipley is the most plausible candidate for two reasons: he has pitched really well at Triple-A Reno this season, and his starts align with Walker’s.
The 26-year-old Shipley is 2-0 with a 2.38 ERA in two starts for the Aces this season. His K/BB ratio of 9/4 is not ideal, and neither is his .267 opponents batting average and his 12 hits in 11.1 innings, but Shipley has found a way to keep teams off the scoreboard, allowing only 3 earned runs.
Shipley had a rough year at the major league level in 2017, but he has experience and finished strong, pitching to his lowest ERA (4.50) and opponents batting average (.258) in September.
Koch is another option to start on the D-Backs 40-man roster.
The 27-year-old Koch has made one start for Reno and did not allow a run in 6 innings. The right-hander already has pitched for the D-Backs this season, tossing two scoreless innings in relief on April 7 against the Cardinals in St. Louis.
Koch also has starting experience at the big league level. He made seven appearances (two starts) two years ago for the D-Backs and finished 1-1 with a 2.00 ERA.
Scribner was acquired by Mike Hazen for this reason — to provide the D-Backs with starting pitching depth.
He has not established a track record of success at the major league level, but the 26-year-old right-hander made four starts for the Los Angeles Angels last season and went 2-1 with a 4.18 ERA.
The most unlikely candidate is McFarland. He tossed four scoreless innings in relief of Walker.
His ability to get groundballs and give the team length makes him a possibility, but manager Torey Lovullo might opt to keep McFarland in his role as long reliever, just in case one of the D-Backs starters before Walker’s turn has a short outing.