The hard-throwing 22-year-old is Seattle's top pitching prospect and ranked No. 6 among all prospects by MLB.com. He made three starts earlier this season after getting a late start due to right shoulder problems in Spring Training, but spent most of the second half with Triple-A Tacoma before being called up Sept. 1 to help bolster the bullpen.
Walker has a 1.93 ERA in three relief appearances this month (two earned runs in 9 1/3 innings) and is 1-2 with a 2.96 ERA in six outings for the year.
It's been a challenging season for the youngster, who was expected to make the season-opening rotation until he arrived at camp with a sore shoulder and subsequently had some command issues when he did get a shot in Seattle. But he now has at least two starts to show what he can do -- including next Wednesday in Toronto -- with the Mariners pushing for their first postseason appearance since 2001.
"Obviously with the concerns we have with Elias, it's an opportunity for him to step up and move into the rotation," manager Lloyd McClendon said. "I think in a lot of ways it's a real good experience for him. Obviously this has been a tough year for him in a lot of different ways. I think he's starting to grow up a little bit from a mental standpoint and starting to 'get it', so to speak. This is good for him."
McClendon has taken a tough-love approach with Walker this season, pushing him hard and speaking critically at times of his performances in Triple-A. But he said he likes what he's seen of late from Walker on the mound and with his work.
"There's a natural progression that he needs to take, and I think he's starting to take it," McClendon said. "Sometimes young players can believe the hype that you guys throw on them and it can get in the way of their development. I think he's finally got to the point where he's put that aside and he's going out and concentrating on what is going to make him better. And that's healthy progression, healthy growth, from a pitching standpoint."
Elias was scheduled to pitch Sunday, but Walker has been slotted into Friday's game since his last outing was two innings on Sunday against the A's and this allows Chris Young and Hisashi Iwakuma to be pushed back to Saturday and Sunday in Houston at a time of the season when the extra day can be beneficial.
"He slots right in and the other two guys get an extra day, so it just makes sense," McClendon said. "They need [the rest]. They all need it. This is a grind."
Walker will be facing a familiar foe in Houston, as three of his six career starts have been against the Astros (2-0, 2.81 ERA), including his lone win this year in his season debut at Minute Maid Park in late June.
Elias flew home to Seattle for an MRI on his elbow Wednesday, but the club was still awaiting results in the hours before Thursday's series finale.