TOKYO -- Mariners reliever Shawn Armstrong didn't think much of the tightness he felt in his left side during his last Cactus League appearance the day before boarding a flight for Japan.

The hard-throwing right-hander threw a scoreless inning in the Wednesday night game against the Giants, then hurried with his teammates to get settled in for the 12-hour flight to Tokyo the next morning.

But once in Japan, the 28-year-old felt increased pain when he tried to play catch during a light workout. An MRI showed a Grade 1 strain of his left oblique, and suddenly Armstrong's promising season slammed to a halt before it could even begin.

"I don't think frustration is the word," Armstrong said in the Mariners' clubhouse at the Tokyo Dome prior to Wednesday's Opening Day game against the A's. "It's very, very frustrating after working so hard this offseason on the things we needed to work on to come into spring healthy and ready to help this ballclub win.

"I felt I was in a really good spot to break for the season going into that last game. It was an unfortunate event and all I can do now is help these guys in any way I can while I'm here and support them."

Oblique issues tend to linger for pitchers if they're not careful, so the Mariners will be cautious not to rush Armstrong despite their need for experienced bullpen arms. While Grade 1 is the least severe strain, manager Scott Servais would only say Armstrong will be sidelined "at least a few weeks."

Armstrong was placed on the 10-day injured list, but he undoubtedly will be out longer even though he said the swelling has already subsided and the area doesn't hurt except when he threw.

"That's kind of key to my position," he acknowledged. "It's one of those injuries you can't rush back. That's the one thing I have to accept. You can kind of be a man about certain things and fight through things, but I've been told over and over this isn't one of them. I just have to trust the training staff and do whatever I can do around that to get myself ready for when I can pick up a baseball again."

That won't be until the Mariners return to Seattle at the earliest. Armstrong figured to be one of Servais' late-inning options after pitching extremely well in the final month last season after being called up from Triple-A Tacoma, posting a 1.23 ERA with one save in 14 appearances.

"I'm hungry and ready to get going," Armstrong said. "This is a little setback, but the good thing is it's early. I know I won't be throwing Opening Day, but I'll take it one step at a time and the sooner the better."

Mallex on the mend

Center fielder Mallex Smith continues working out in Arizona, as has been hitting in Minor League games in order to regain his timing at the plate after recovering from a strained right elbow that wiped out most of his Spring Training.

Smith wasn't placed on the injured list, so he could be able to join the Mariners as soon as they return to Seattle for their home opener on March 28 if he's deemed ready. That might be a stretch, however, since he's yet to play in the field.

The Mariners will test Smith in the exhibition games against the Padres at T-Mobile Park next Monday and Tuesday to see if he's ready.

"We do want to see Mallex get out there and play defense and how he bounces back a couple days in a row," Servais said. "Right now, the reports have been really good. He's progressing nicely with no setbacks at all as far as his throwing arm is concerned.

"But when we activate him, we want to make sure he can go out and play multiple days in a row. Until we get back in Seattle, we won't know a ton more. But we'll see what it looks like in the exhibition games against the Padres."

Lewis lights it up in Arizona

While the Mariners' Major Leaguers are in Japan, the team still has three Cactus League contests in Arizona that are being played by their Minor Leaguers. Outfielder Kyle Lewis continued his strong spring with a home run and double in a 6-4 loss to the Cubs in Mesa on Tuesday in the first of those games.

Lewis, the team's No. 7 prospect per MLB Pipeline, is batting .429 (9-for-21) with three doubles and three homers in 10 Cactus League games.

First baseman Evan White, the team's No. 4 prospect, was scratched from the game due to illness.

Justin Dunn, the No. 3 prospect acquired from the Mets last winter, will start Thursday's 6:40 p.m. PT contest against the Reds at Peoria Stadium.

Up next

Yusei Kikuchi will make his Major League debut for the Mariners in Thursday's second game of the Opening Series, another 2:35 a.m. PT start at the Tokyo Dome. The 27-year-old southpaw, a three-time All-Star for the Seibu Lions in Japan, will face A's right-hander Marco Estrada (7-14, 5.64 ERA last year for the Blue Jays). The game will be televised live by ESPN and rebroadcast on ROOT Sports in Seattle at 6:35 p.m. PT.