Who will the Mariners start for Tuesday’s game in Texas? Not Justus Sheffield

SEATTLE – Manager Scott Servais and the Mariners are “inching” toward making a decision on who will start Tuesday in Texas. But this much is certain, it won’t be top prospect Justus Sheffield.

The talented lefty pitched 5 2/3 innings on Friday night in Reno for Class AAA Tacoma. Sheffield allowed three runs on five hits with three walks and six strikeouts in Tacoma’s 10-6 win over the Aces.

The Mariners will likely either select the minor-league contract of veteran left-hander Tommy Milone from Tacoma and add him to the active roster or else have a bullpen start to cover the innings.

Why not Sheffield?

He has struggled at times with fastball command and pitch efficiency. Servais saw it first hand when Sheffield was called up to piggy-back off of Yusei Kikuchi’s one-inning start on April 26 vs. the Rangers. Sheffield needed 75 pitches to get through three innings, walking four batters and striking out three while giving up two runs on two hits.

The plan has always been for Sheffield to join the rotation at some point this season. But this isn’t the right time.

“I think when we get to the point where we call Justus up, we’d like to call him up and leave him here and let him go,” Servais said. “I don’t want to call him up and give him one or two outings and then go back and forth (with Tacoma). He’s working on things right now.”

Those things include a few mechanical tweaks to find some consistency with fastball location as well as the continued effort to make the changeup a strong secondary pitch to go with his slider. The reports from Tacoma are encouraging. Sheffield has shown signs of progress in getting more efficient and getting ahead of hitters earlier in counts.

“There’s a lot of positives there,” Servais said.

In seven starts and one relief appearance, Sheffield is 1-2 with a 4.38 ERA. In 37 innings pitched, he’s walked a whopping 28 batter to go with 33 strikeouts.

“Sometimes getting caught up in the line score in the PCL right now is dangerous,” Servais said. “We’re not at the games, so it’s all we can really look at. So you really have to go with the people who are there, giving us reports on the stuff, the command, the hits.”

The reason it’s dangerous is the decision to go to the same baseball as used at the major-league level. That baseball is much more hitter friendly. Home runs at the Triple A level are expected to be at an all-time high because of the switch. It’s even more pronounced in the hitter-friendly parks and cities of the Pacific Coast League where dry air and altitude already skewed the numbers.

“If you look at the numbers in the PCL this year, they are off the chart,” he said. “They’re playing with the Major League baseball in Triple-A this year and it’s changed the game quite a bit. I think it’s a good thing for the pitchers to not have to make an adjustment when they come to the big leagues with the ball, but the numbers are up dramatically.”