Baseball notebook: Mariners cautious with Taijuan Walker

The plot thickens regarding the Mariners’ depleted rotation.

Right-hander Taijuan Walker headed back Monday to Seattle to undergo a further examination, likely to include a magnetic resonance imaging (MRI) test, in an effort to find answers regarding the tendinitis in his right foot.

“We just want to make sure,” manager Scott Servais said prior the series opener at Detroit. “He tested out OK today (in an examination by trainer Rick Griffin), but I think we’d all feel more comfortable if we had some pictures of it.”

Walker made an early exit Sunday for a second straight start because of posterior tibial tendinitis — inflammation in the tendon that attaches the calf muscle to the bones on the inside of the foot.

Walker’s return to Seattle dims the likelihood that he will make his scheduled start Friday against the St. Louis Cardinals at Safeco Field. He would likely need to throw a bullpen workout Wednesday without difficulty to gain clearance.

“Maybe we can figure out a way to jimmy the rotation to push him back a day or two,” Servais said. “So maybe we wouldn’t have to DL him. I’m not sure. I don’t want to get ahead of myself.”

Walker, 23, is just 3-6 despite a 3.45 ERA in 14 starts. His tendinitis stems from flat feet, which increases stress he places on the arch in his right foot as he pushes off the rubber.

The Mariners are already operating without two of their five starting pitchers.

Right-hander Felix Hernandez hasn’t pitched since May 27 because of a strained right calf muscle. Lefty Wade Miley is nursing an impingement in his shoulder, which forced him to the disabled list and is unavailable until at least June 28.

“It’s tough,” Servais admitted. “We will get Wade back. That helps. Felix is feeling better. Good report today. Moving in the right direction.”

Having already summoned James Paxton and Adrian Sampson from Triple-A Tacoma to patch their rotation, the Mariners could have just-acquired Zach Lee atop their list of alternatives if Walker can’t start Friday against Cardinals.

Seattle obtained Lee from the Dodgers in a Sunday trade for shortstop Chris Taylor.

While the Mariners assigned Lee, a right-hander, to Tacoma, he is on the 40-man roster, which means he can be recalled to the big leagues without the need for a corresponding space-clearing move.

Marquee matchup scratched

The Nationals scratched unbeaten right-hander Stephen Strasburg with an upper back strain, spoiling his scheduled showdown with Clayton Kershaw in Los Angeles about an hour before the first pitch.

Yusmeiro Petit got the start in place of Strasburg (10-0), who was due to face Kershaw (10-1) for the first time in the aces’ major league careers.

The Cubs placed center fielder Dexter Fowler on the 15-day disabled list with a right hamstring injury.