SEATTLE — The decision this week by the Mariners to shift right-hander Edwin Diaz, generally viewed as their top pitching prospect, to a relief role stemmed from a simple evaluation.
The Mariners believe Diaz, 22, projects as a back-of-the-rotation starter but see him as a potential impact reliever who could, possibly, help the big-league club this season at some point.
"He has been dominant (for Jackson) at the Double-A level to start the season," general manager Jerry Dipoto said. "We felt that as a starter, he’s mostly 90-94 (mph) with a good slider.
"What happens when we dump him into the bullpen, we have a chance to get that back-end dynamic arm. Does that supersede the ceiling that he would have as a starter?"
Diaz made the switch Tuesday night by pitching one inning for the Generals in a 3-2 victory at Birmingham (White Sox).
"He had a really clean inning," Dipoto said. "Thirteen pitches with nine strikes and he was up to 98 miles an hour and sitting on 96. He was looking every bit of what we were hoping it would look like.
"Now we have to see if it looks like that in outing No. 2."
Diaz was the Mariners’ third-round pick in 2012 and quickly established himself as one of the organization’s top prospects by compiling a 1.43 ERA in 13 starts in 2013 at short-season Pulaski in the Appalachian League.
A year later, he posted a 3.34 ERA in 24 starts at Lo-A Clinton and, in 2015, had a 1.70 ERA in seven starts at Hi-A Bakersfield in the hitter-friendly California League.
That quick start at Bakersfield earned him a promotion to Jackson, where he endured an inconsistent four months: 5-10 with a 4.57 ERA in 20 starts. This season, he was 2-3 and 3.10 in five starts before Tuesday’s shift to the bullpen.
"Edwin has plus fastball velocity, plus fastball life and what at times is a plus breaking ball," Dipoto said. "The change-up has never really been easy for him. It’s not the most conventional arm action and delivery you’ll ever see.
"So the likelihood of him picking up that third pitch is maybe a little bit more remote."
Having that third pitch is less important as a reliever.
Injured relievers Joaquin Benoit and Charlie Furbush each took a major step toward returning to active duty prior to Wednesday’s game by flashing positive results in bullpen workouts.
Benoit is now ticketed to pitch this weekend in a simulated game and, barring a setback, should be activated from the disabled list prior to Tuesday’s series opener at Baltimore.
Plans call for Furbush to pitch against hitters in a controlled session this weekend at Triple-A Tacoma before heading to Arizona to commence what will amount to a spring-like progression of building up his innings and endurance.
"Furbush was extremely aggressive through the ball," Dipoto said. "Both of them were very happy after they threw. That was the best we’ve seen Joaquin Benoit since signed him. The ball was really carrying out of his hand."
Benoit, 38, hasn’t pitched since April 21 because of shoulder inflammation. If he returns as expected, the Mariners are likely to clear space on their roster by optioning reliever Mayckol Guaipe back to Tacoma.
Furbush, 30, could be ready to rejoin the Mariners prior to the end of the month.
He underwent blood-injection therapy last month after opening the season on the disabled list because of lingering day-after tightness in his recovery from biceps tendinitis and a slight tear in his rotator cuff.
"If we have the opportunity to add those two before long," Dipoto said, "it really helps our bullpen, which I think has already been a positive."
The Mariners entered Wednesday’s series finale against Tampa Bay with a 2.37 bullpen ERA, which ranked first in the majors.
PLAYING IT CLOSE
Even before spring training started, manager Scott Servais predicted the Mariners would play a lot of one-run games.
So far, he’s been right.
The Mariners have played 13 one-run games, which leads all American League clubs. The Mariners are 8-5 in those games, including seven straight victories after Wednesday’s 6-5 victory over Tampa Bay in 11 innings.
"Good teams have to play a lot of one-run games," Servais said, "and they have to win them. I thought we were going to be a good team. Talking about it — you throw it out on the table. Here’s what it is. Let’s see how we do.
"Now, we didn’t start off that great. We lost some one-run games early. It’s OK. We’re just going to have to be comfortable being in them.
"Our starting rotation is going to keep us in games. Our bullpen has been very consistent. They’re going to keep it tight. You’re going to be in those games."
STAYING IN LINE
Even with two upcoming open dates, Thursday and Monday, Servais has no plans to alter his rotation. Nobody will be skipped in order to keep somebody else on the regular five-day schedule.
"I’ll stay with what I’ve said all along," Servais reiterated. "Picking up that extra day helps guys. It doesn’t get them off of their rhythm. We don’t really have anyone to skip in my mind.
"I think all of our guys are throwing the ball pretty well. So we’ll just give them the extra day and keep building on that."
Servais previously indicated his approach might change later in the season when match-ups become more important.
Double-A Jackson first baseman D.J. Peterson is showing some encouraging signs in a 12-for-34 surge (.353) over his last nine games. His overall average is up to .243 with two homers and 16 RBIs in 29 games.
Peterson, 24, was the Mariners’ first-round pick in 2013 and produced a strong 2014 season, when he batted .297 with 31 homers and 111 RBIs in 123 games at Hi-A High Desert and Jackson.
But he slumped badly last season to .223 with seven homers and 44 RBIs in 96 games, including 92 at Jackson.
It was 32 years ago Thursday — May 12, 1984 — that right-hander Jim Beattie pitched a six-hit shutout in a 5-0 victory over the Yankees, his former team, in New York.
Rookie first baseman Alvin Davis went 2-for-2 with a two-run double but suffered a broken nose in the fifth inning on a bad-hop single off the bat of Steve Kemp.
Davis missed four games before returning to the lineup.
Beattie, now 61, was 43-72 with a 4.14 ERA in seven years with the Mariners after arriving as part of a six-player trade with the Yankees on Nov. 1, 1979. He served as the Mariners’ farm director from 1990-95.
The Mariners have an open date Thursday before concluding their homestand with three weekend games against the Los Angeles Angels at Safeco Field.
Right-hander Nathan Karns (3-1 with a 3.38 ERA) will face LA right-hander Nick Tropeano (1-2, 3.69) at 7:10 p.m. Friday in the series opener. The game can be seen on Root Sports Northwest and heard on 710 ESPN.
Bob Dutton: @TNT_Mariners
AMERICAN LEAGUE RECORDS IN ONE-RUN GAMES
Seattle: 12 (7-5)*
Cleveland: 12 (5-7)
Oakland: 11 (5-6)
Minnesota: 11 (4-7)
Toronto: 10 (3-7)
Chicago: 9 (6-3)
Kansas City: 9 (5-4)
New York: 9 (4-5)
Detroit: 8 (4-4)
Houston: 8 (3-5)
Texas: 7 (4-3)
Los Angeles: 7 (3-4)
Baltimore: 6 (4-2)
Boston: 6 (3-3)
Tampa Bay: 5 (3-2)
* — now 8-5 in 13 one-run games after Wednesday’s 6-5 victory over Tampa Bay in 11 innings.